diff --git a/Interview Preparation Kit - CPP/01. Warm-up Challenges/001. Sock Merchant.cpp b/Interview Preparation Kit - CPP/01. Warm-up Challenges/001. Sock Merchant.cpp
new file mode 100644
index 00000000..09f14c1f
--- /dev/null
+++ b/Interview Preparation Kit - CPP/01. Warm-up Challenges/001. Sock Merchant.cpp	
@@ -0,0 +1,25 @@
+// Problem: https://www.hackerrank.com/challenges/sock-merchant/problem
+// Score: 10
+
+
+#include <iostream>
+
+
+int main() {
+    int n, element;
+    int arr[101] = {0};
+    int ans = 0;
+
+    std::cin >> n;
+
+    for (int i = 0; i < n; i++) {
+        std::cin >> element;
+        arr[element]++;
+
+        ans += arr[element] / 2;
+        arr[element] = arr[element] % 2;
+    }
+
+    std::cout << ans << std::endl;
+    return 0;
+}
diff --git a/Interview Preparation Kit - CPP/01. Warm-up Challenges/002. Counting Valleys.cpp b/Interview Preparation Kit - CPP/01. Warm-up Challenges/002. Counting Valleys.cpp
new file mode 100644
index 00000000..758a31c0
--- /dev/null
+++ b/Interview Preparation Kit - CPP/01. Warm-up Challenges/002. Counting Valleys.cpp	
@@ -0,0 +1,34 @@
+// Problem: https://www.hackerrank.com/challenges/counting-valleys/problem
+// Score: 15
+
+#include <iostream>
+#include <string>
+using namespace std;
+
+int main() {
+    int n;
+    cin >> n;
+
+    string str;
+    cin >> str;
+
+    int ans = 0;
+
+    int current_level = 0;
+
+    for (char c: str){
+        if (c == 'D') {
+            if (current_level == 0){
+                ans++;
+            }
+
+            current_level--;
+        }
+
+        else if (c == 'U') current_level++;
+    }
+
+    cout << ans;
+
+    return 0;
+}
diff --git a/Interview Preparation Kit - CPP/01. Warm-up Challenges/003. Jumping on the Clouds.cpp b/Interview Preparation Kit - CPP/01. Warm-up Challenges/003. Jumping on the Clouds.cpp
new file mode 100644
index 00000000..bfaf7a9c
--- /dev/null
+++ b/Interview Preparation Kit - CPP/01. Warm-up Challenges/003. Jumping on the Clouds.cpp	
@@ -0,0 +1,34 @@
+// Problem: https://www.hackerrank.com/challenges/jumping-on-the-clouds/problem
+// Score: 20
+
+
+#include <iostream>
+#include <vector>
+using namespace std;
+
+int main(){
+    int n;
+    cin >> n;
+
+    int element;
+    vector<int> arr;
+
+    while (cin >> element){
+        arr.push_back(element);
+    }
+
+    int ans = 0;
+    int position = 0;
+
+    while (position < n - 1){
+        position ++;
+        if (position + 1 <= n - 1 && arr[position + 1] != 1){
+            position ++;
+        }
+        ans ++;
+    }
+
+    cout << ans;
+
+    return 0;
+}
diff --git a/Interview Preparation Kit - CPP/01. Warm-up Challenges/004. Repeated String.cpp b/Interview Preparation Kit - CPP/01. Warm-up Challenges/004. Repeated String.cpp
new file mode 100644
index 00000000..5a64d611
--- /dev/null
+++ b/Interview Preparation Kit - CPP/01. Warm-up Challenges/004. Repeated String.cpp	
@@ -0,0 +1,32 @@
+// Problem: https://www.hackerrank.com/challenges/repeated-string/problem
+// Score: 20
+
+
+#include <iostream>
+#include <string>
+
+using namespace std;
+
+
+long long count(string const & str){
+    long long ans = 0;
+    for (const char & c: str){
+        ans += c == 'a';
+    }
+    return ans;
+}
+
+
+int main(){
+    string str;
+    cin >> str;
+
+    long long n;
+    cin >> n;
+
+    long long ans = 0;
+    ans = n / str.size() * count(str) + count(str.substr(0, n % str.size()));
+
+    cout << ans;
+    return 0;
+}
diff --git a/Interview Preparation Kit - CPP/01. Warm-up Challenges/CMakeLists.txt b/Interview Preparation Kit - CPP/01. Warm-up Challenges/CMakeLists.txt
new file mode 100644
index 00000000..8fcc02e5
--- /dev/null
+++ b/Interview Preparation Kit - CPP/01. Warm-up Challenges/CMakeLists.txt	
@@ -0,0 +1,8 @@
+cmake_minimum_required (VERSION 3.8)
+
+project(warm-up)
+
+add_executable(task-1 "001. Sock Merchant.cpp")
+add_executable(task-2 "002. Counting Valleys.cpp")
+add_executable(task-3 "003. Jumping on the Clouds.cpp")
+add_executable(task-4 "004. Repeated String.cpp")
diff --git a/Interview Preparation Kit - CPP/02. Arrays/001. 2D Array - DS.cpp b/Interview Preparation Kit - CPP/02. Arrays/001. 2D Array - DS.cpp
new file mode 100644
index 00000000..2e4ef6cc
--- /dev/null
+++ b/Interview Preparation Kit - CPP/02. Arrays/001. 2D Array - DS.cpp	
@@ -0,0 +1,38 @@
+// Problem: https://www.hackerrank.com/challenges/2d-array/problem
+// Score: 15
+
+
+#include <iostream>
+using namespace std;
+
+int hourglass_sum(int arr[6][6], int i, int j){
+    int ans = 0;
+    ans = arr[i][j] + arr[i][j + 1] + arr[i][j + 2] +
+            arr[i + 1][j + 1] +
+            arr[i + 2][j] + arr[i + 2][j + 1] + arr[i + 2][j + 2];
+    return ans;
+}
+
+
+int main(){
+
+    int arr[6][6];
+
+    for (auto & i : arr){
+        for (int & j : i){
+            cin >> j;
+        }
+    }
+
+    int ans = -1000;
+    for (int i = 0; i < 4; i++){
+        for (int j = 0; j < 4; j++){
+            if (hourglass_sum(arr, i, j) > ans){
+                ans = hourglass_sum(arr, i, j);
+            }
+        }
+    }
+
+    cout << ans;
+    return 0;
+}
diff --git a/Interview Preparation Kit - CPP/02. Arrays/002. Arrays - Left Rotation.cpp b/Interview Preparation Kit - CPP/02. Arrays/002. Arrays - Left Rotation.cpp
new file mode 100644
index 00000000..1595386c
--- /dev/null
+++ b/Interview Preparation Kit - CPP/02. Arrays/002. Arrays - Left Rotation.cpp	
@@ -0,0 +1,27 @@
+// Problem: https://www.hackerrank.com/challenges/ctci-array-left-rotation/problem
+// Score: 20
+
+
+#include <iostream>
+#include <vector>
+using namespace std;
+
+int main(){
+    int n, d;
+
+    cin >> n;
+    cin >> d;
+
+    vector<int> arr;
+    for (int i = 0; i < n; i++){
+        int tmp;
+        cin >> tmp;
+        arr.push_back(tmp);
+    }
+
+    for (int i = 0; i < n; i++){
+        cout << arr[(i + d) % n] << " ";
+    }
+
+    return 0;
+}
diff --git a/Interview Preparation Kit - CPP/02. Arrays/003. New Year Chaos.cpp b/Interview Preparation Kit - CPP/02. Arrays/003. New Year Chaos.cpp
new file mode 100644
index 00000000..6c073993
--- /dev/null
+++ b/Interview Preparation Kit - CPP/02. Arrays/003. New Year Chaos.cpp	
@@ -0,0 +1,56 @@
+// Problem: https://www.hackerrank.com/challenges/new-year-chaos/problem
+//  Score: 40
+
+#include <iostream>
+#include <vector>
+using namespace std;
+
+
+bool check_sorted(vector<int> & arr){
+    bool ans = true;
+    for (int i = 0; i < arr.size() - 1; i++){
+        if (arr[i] > arr[i + 1]){
+            ans = false;
+        }
+    }
+    return ans;
+}
+
+
+int main(){
+    int t;
+    cin >> t;
+
+    for (int i = 0; i < t; i++){
+        int n;
+        cin >> n;
+        vector<int> arr;
+
+        for (int j = 0; j < n; j++){
+            int tmp;
+            cin >> tmp;
+            arr.push_back(tmp);
+        }
+
+        int ans = 0;
+
+        for (int j = 0; j < 2; j++){
+            for (int k = arr.size() - 1; k > 0; k--){
+                if (arr[k] < arr[k - 1]){
+                    swap(arr[k], arr[k - 1]);
+                    ans++;
+                }
+            }
+        }
+
+        if (check_sorted(arr)){
+            cout << ans << endl;
+        }
+        else {
+            cout << "Too chaotic" << endl;
+        }
+
+    }
+
+    return 0;
+}
diff --git a/Interview Preparation Kit - CPP/02. Arrays/004. Minimum Swaps 2.cpp b/Interview Preparation Kit - CPP/02. Arrays/004. Minimum Swaps 2.cpp
new file mode 100644
index 00000000..dbe45816
--- /dev/null
+++ b/Interview Preparation Kit - CPP/02. Arrays/004. Minimum Swaps 2.cpp	
@@ -0,0 +1,36 @@
+// Problem: https://www.hackerrank.com/challenges/minimum-swaps-2/problem
+// Score: 40
+
+
+#include <iostream>
+#include <vector>
+using namespace std;
+
+
+int main(){
+    int n;
+    cin >> n;
+    vector<int> arr;
+
+    for (int i = 0; i < n; i++){
+        int tmp;
+        cin >> tmp;
+        arr.push_back(tmp - 1);
+    }
+
+    int i = 0;
+    int ans = 0;
+    while (i < n){
+        if (arr[i] != i){
+            swap(arr[i], arr[arr[i]]);
+            ans++;
+        }
+        else{
+            i++;
+        }
+    }
+
+    cout << ans;
+
+    return 0;
+}
diff --git a/Interview Preparation Kit - CPP/02. Arrays/005. Array Manipulation.cpp b/Interview Preparation Kit - CPP/02. Arrays/005. Array Manipulation.cpp
new file mode 100644
index 00000000..99ca243b
--- /dev/null
+++ b/Interview Preparation Kit - CPP/02. Arrays/005. Array Manipulation.cpp	
@@ -0,0 +1,36 @@
+// Problem: https://www.hackerrank.com/challenges/crush/problem
+// Score: 60
+
+
+#include <iostream>
+#include <vector>
+using namespace std;
+
+
+int main(){
+    int n, m;
+    cin >> n >> m;
+
+    vector<long long int> arr(n, 0);
+
+    for (int i = 0; i < m; i++){
+        int start, finish, value;
+        cin >> start >> finish >> value;
+        arr[start - 1] += value;
+        arr[finish] -= value;
+    }
+
+    long long int ans = 0;
+    long long int current = 0;
+
+    for (int value: arr){
+        current += value;
+        if (current > ans){
+            ans = current;
+        }
+    }
+
+    cout << ans;
+
+    return 0;
+}
diff --git a/Interview Preparation Kit - CPP/02. Arrays/CMakeLists.txt b/Interview Preparation Kit - CPP/02. Arrays/CMakeLists.txt
new file mode 100644
index 00000000..61060a89
--- /dev/null
+++ b/Interview Preparation Kit - CPP/02. Arrays/CMakeLists.txt	
@@ -0,0 +1,9 @@
+cmake_minimum_required (VERSION 3.8)
+
+project(arrays)
+
+add_executable(task-1 001.\ 2D\ Array\ -\ DS.cpp)
+add_executable(task-2 002.\ Arrays\ -\ Left\ Rotation.cpp)
+add_executable(task-3 003.\ New\ Year\ Chaos.cpp)
+add_executable(task-4 004.\ Minimum\ Swaps\ 2.cpp)
+add_executable(task-5 005.\ Array\ Manipulation.cpp)
diff --git a/Interview Preparation Kit - CPP/03. Dictionaries and Hashmaps/001. Hash Tables - Ransom Note.cpp b/Interview Preparation Kit - CPP/03. Dictionaries and Hashmaps/001. Hash Tables - Ransom Note.cpp
new file mode 100644
index 00000000..e777fc35
--- /dev/null
+++ b/Interview Preparation Kit - CPP/03. Dictionaries and Hashmaps/001. Hash Tables - Ransom Note.cpp	
@@ -0,0 +1,48 @@
+// Problem: https://www.hackerrank.com/challenges/ctci-ransom-note/problem
+// Score: 25
+
+#include <iostream>
+#include <string>
+#include <map>
+using namespace std;
+
+
+int main(){
+    int m, n;
+    cin >> m >> n;
+
+    map<string, int> magazine;
+
+    for (int i = 0; i < m; i++) {
+        string word;
+        cin >> word;
+
+        if (magazine.find(word) == magazine.end()){
+            magazine[word] = 1;
+        }
+        else {
+            magazine[word]++;
+        }
+    }
+
+
+    bool ans = true;
+    for (int i = 0; i < n; i++){
+        string word;
+        cin >> word;
+
+        if (magazine.find(word) == magazine.end() || magazine[word] == 0){
+            ans = false;
+            break;
+        }
+        else {
+            magazine[word]--;
+        }
+    }
+
+
+    if (ans) cout << "Yes" << endl;
+    else cout << "No" << endl;
+
+    return 0;
+}
diff --git a/Interview Preparation Kit - CPP/03. Dictionaries and Hashmaps/002. Two Strings.cpp b/Interview Preparation Kit - CPP/03. Dictionaries and Hashmaps/002. Two Strings.cpp
new file mode 100644
index 00000000..720b0630
--- /dev/null
+++ b/Interview Preparation Kit - CPP/03. Dictionaries and Hashmaps/002. Two Strings.cpp	
@@ -0,0 +1,38 @@
+// Problem: https://www.hackerrank.com/challenges/two-strings/problem
+// Score: 25
+
+
+#include <iostream>
+#include <set>
+#include <string>
+using namespace std;
+
+
+int main(){
+    int p;
+    cin >> p;
+
+    for (int i = 0; i < p; i++){
+        string s1, s2;
+        cin >> s1 >> s2;
+
+        set<char> letters;
+
+        for (char c: s1){
+            letters.insert(c);
+        }
+
+        bool ans = false;
+        for (char c: s2){
+            if (letters.find(c) != letters.end()){
+                ans = true;
+                break;
+            }
+        }
+
+        if (ans) cout << "YES" << endl;
+        else cout << "NO" << endl;
+    }
+
+    return 0;
+}
diff --git a/Interview Preparation Kit - CPP/03. Dictionaries and Hashmaps/003. Sherlock and Anagrams.cpp b/Interview Preparation Kit - CPP/03. Dictionaries and Hashmaps/003. Sherlock and Anagrams.cpp
new file mode 100644
index 00000000..f8c664b1
--- /dev/null
+++ b/Interview Preparation Kit - CPP/03. Dictionaries and Hashmaps/003. Sherlock and Anagrams.cpp	
@@ -0,0 +1,45 @@
+// Problem: https://www.hackerrank.com/challenges/sherlock-and-anagrams/problem
+// Score: 50
+
+
+#include <iostream>
+#include <string>
+#include <algorithm>
+#include <map>
+using namespace std;
+
+
+int main(){
+    int n;
+    cin >> n;
+    for (int t = 0; t < n; t++){
+        string str;
+        cin >> str;
+
+        map<string, int> lib;
+
+        for (int i = 1; i < str.size(); i++){
+            for (int j = 0; j < str.size() - i + 1; j++){
+                string tmp = str.substr(j, i);
+                sort(tmp.begin(), tmp.end());
+
+                if (lib.find(tmp) != lib.end()){
+                    lib[tmp]++;
+                }
+                else {
+                    lib[tmp] = 1;
+                }
+
+            }
+        }
+
+        int ans = 0;
+        for (auto const & el: lib){
+            ans += el.second * (el.second - 1) / 2;
+        }
+
+        cout << ans << endl;
+    }
+
+    return 0;
+}
\ No newline at end of file
diff --git a/Interview Preparation Kit - CPP/03. Dictionaries and Hashmaps/004. Count Triplets.cpp b/Interview Preparation Kit - CPP/03. Dictionaries and Hashmaps/004. Count Triplets.cpp
new file mode 100644
index 00000000..218ed8ed
--- /dev/null
+++ b/Interview Preparation Kit - CPP/03. Dictionaries and Hashmaps/004. Count Triplets.cpp	
@@ -0,0 +1,35 @@
+// Problem: https://www.hackerrank.com/challenges/count-triplets-1/problem
+// Score: 25
+
+
+#include <iostream>
+#include <map>
+using namespace std;
+
+
+struct custom_int{
+    long long int value = 0;
+};
+
+
+int main(){
+    int n, r;
+    cin >> n >> r;
+    map<long long int, custom_int> arr2;
+    map<long long int, custom_int> arr3;
+
+    long long int ans = 0;
+
+    for (int i = 0; i < n; i++) {
+        int tmp;
+        cin >> tmp;
+
+        ans += arr3[tmp].value;
+        arr3[tmp * r].value += arr2[tmp].value;
+        arr2[tmp * r].value++;
+    }
+
+    cout << ans;
+
+    return 0;
+}
diff --git a/Interview Preparation Kit - CPP/03. Dictionaries and Hashmaps/005. Frequency Queries.cpp b/Interview Preparation Kit - CPP/03. Dictionaries and Hashmaps/005. Frequency Queries.cpp
new file mode 100644
index 00000000..6da94f4f
--- /dev/null
+++ b/Interview Preparation Kit - CPP/03. Dictionaries and Hashmaps/005. Frequency Queries.cpp	
@@ -0,0 +1,66 @@
+// Problem: https://www.hackerrank.com/challenges/frequency-queries/problem
+// Score: 40
+
+
+#include <map>
+using namespace std;
+
+
+struct default_long_long_int{
+    int value = 0;
+};
+
+
+struct custom_struct{
+public:
+    void insert(int num){
+        arr[num].value++;
+        frequencies[arr[num].value].value++;
+        frequencies[arr[num].value - 1].value--;
+    }
+
+    void remove(int num){
+        if (arr[num].value != 0){
+            arr[num].value--;
+            frequencies[arr[num].value].value++;
+            frequencies[arr[num].value + 1].value--;
+        }
+
+        if (arr[num].value == 0){
+            arr.erase(num);
+        }
+    };
+
+    int check(int value){
+        if (frequencies[value].value != 0) return 1;
+        else return 0;
+    }
+
+private:
+    map<int, default_long_long_int> arr;
+    map<int, default_long_long_int> frequencies;
+};
+
+
+int main(){
+    int q;
+    scanf("%d",&q);
+    custom_struct arr;
+
+    for (int i = 0; i < q; i++){
+        int command, value;
+        scanf("%d",&command);
+        scanf("%d",&value);
+
+        if (command == 1){
+            arr.insert(value);
+        }
+        if (command == 2){
+            arr.remove(value);
+        }
+        if (command == 3){
+            printf("%d \n", arr.check(value));
+        }
+    }
+    return 0;
+}
diff --git a/Interview Preparation Kit - CPP/03. Dictionaries and Hashmaps/CMakeLists.txt b/Interview Preparation Kit - CPP/03. Dictionaries and Hashmaps/CMakeLists.txt
new file mode 100644
index 00000000..131ca8f7
--- /dev/null
+++ b/Interview Preparation Kit - CPP/03. Dictionaries and Hashmaps/CMakeLists.txt	
@@ -0,0 +1,9 @@
+cmake_minimum_required (VERSION 3.8)
+
+project(dictionaries-and-hashmaps)
+
+add_executable(task-1 001.\ Hash\ Tables\ -\ Ransom\ Note.cpp)
+add_executable(task-2 002.\ Two\ Strings.cpp)
+add_executable(task-3 003.\ Sherlock\ and\ Anagrams.cpp)
+add_executable(task-4 004.\ Count\ Triplets.cpp)
+add_executable(task-5 005.\ Frequency\ Queries.cpp)
\ No newline at end of file
diff --git a/Interview Preparation Kit - CPP/04. Sorting/003. Sorting - Comparator.cpp b/Interview Preparation Kit - CPP/04. Sorting/003. Sorting - Comparator.cpp
new file mode 100644
index 00000000..91a96769
--- /dev/null
+++ b/Interview Preparation Kit - CPP/04. Sorting/003. Sorting - Comparator.cpp	
@@ -0,0 +1,61 @@
+// Problem: https://www.hackerrank.com/challenges/ctci-comparator-sorting
+// Score: 35
+
+
+#include <iostream>
+#include <string>
+#include <algorithm>
+#include <vector>
+using namespace std;
+
+class player {
+public:
+    player(string name, int score): name_(name), score_(score){}
+
+    string get_name() const{
+        return name_;
+    }
+
+    int get_score() const{
+        return score_;
+    }
+
+    void print() const{
+        cout << name_ << " " << score_ << '\n';
+    }
+
+private:
+    string name_;
+    int score_;
+};
+
+
+bool compare_players(player const & p1, player const & p2){
+    if (p1.get_score() > p2.get_score()) return true;
+    else if (p1.get_score() == p2.get_score()) return p1.get_name() < p2.get_name();
+    else return false;
+}
+
+
+int main(){
+    int n;
+    cin >> n;
+
+    vector<player> arr;
+
+    for (int i = 0; i < n; i++){
+        string name;
+        int score;
+        cin >> name >> score;
+        player tmp(name, score);
+        arr.push_back(tmp);
+    }
+
+    sort(arr.begin(), arr.end(), compare_players);
+
+    for (player const & el: arr){
+        el.print();
+    }
+
+    return 0;
+}
diff --git a/Interview Preparation Kit - CPP/04. Sorting/004. Fraudulent Activity Notifications.cpp b/Interview Preparation Kit - CPP/04. Sorting/004. Fraudulent Activity Notifications.cpp
new file mode 100644
index 00000000..070b15e2
--- /dev/null
+++ b/Interview Preparation Kit - CPP/04. Sorting/004. Fraudulent Activity Notifications.cpp	
@@ -0,0 +1,77 @@
+// Problem: https://www.hackerrank.com/challenges/fraudulent-activity-notifications/problem
+// Score: 40
+
+
+#include <iostream>
+#include <queue>
+using namespace std;
+
+
+class moving_median{
+public:
+
+    explicit moving_median(int target_size): target_size(target_size){}
+
+    void add(int value){
+        if (current_size < target_size){
+            current_size++;
+        }
+        else {
+            check_operation(value);
+            arr[q.front()]--;
+            q.pop();
+        }
+
+        arr[value]++;
+        q.push(value);
+    }
+
+    int get_n_notifications(){
+        return n_notifications;
+    }
+
+
+private:
+    void check_operation(int value){
+        if (value >= two_medians()) n_notifications++;
+    };
+
+
+    int find_i_element(int num){
+        int count = 0;
+        for (int i = 0; i < 201; i++){
+            count += arr[i];
+            if (count >= num) return i;
+        }
+        return 200;
+    };
+
+
+    int two_medians(){
+        return (find_i_element(target_size / 2 + 1) + find_i_element(target_size / 2 + target_size % 2));
+    };
+
+
+    int n_notifications = 0;
+    int target_size;
+    int current_size = 0;
+    int arr[201] = {0};
+    queue<int> q;
+};
+
+
+int main(){
+    int n, d;
+    cin >> n >> d;
+
+    moving_median data(d);
+
+    for (int i = 0; i < n; i++){
+        int tmp;
+        cin >> tmp;
+        data.add(tmp);
+    }
+
+    cout << data.get_n_notifications();
+    return 0;
+}
diff --git a/Interview Preparation Kit - CPP/04. Sorting/CMakeLists.txt b/Interview Preparation Kit - CPP/04. Sorting/CMakeLists.txt
new file mode 100644
index 00000000..a2a6ee18
--- /dev/null
+++ b/Interview Preparation Kit - CPP/04. Sorting/CMakeLists.txt	
@@ -0,0 +1,6 @@
+cmake_minimum_required (VERSION 3.8)
+
+project(sorting)
+
+add_executable(task-3 003.\ Sorting\ -\ Comparator.cpp)
+add_executable(task-4 004.\ Fraudulent\ Activity\ Notifications.cpp)
\ No newline at end of file
diff --git a/Interview Preparation Kit - CPP/05. String Manipulation/001. Strings - Making Anagrams.cpp b/Interview Preparation Kit - CPP/05. String Manipulation/001. Strings - Making Anagrams.cpp
new file mode 100644
index 00000000..21f0b7d6
--- /dev/null
+++ b/Interview Preparation Kit - CPP/05. String Manipulation/001. Strings - Making Anagrams.cpp	
@@ -0,0 +1,47 @@
+// Problem: https://www.hackerrank.com/challenges/ctci-making-anagrams/problem
+// Score: 25
+
+
+#include <string>
+#include <iostream>
+#include <algorithm>
+using namespace std;
+
+
+int main(){
+    string s1, s2;
+    cin >> s1 >> s2;
+
+    sort(s1.begin(), s1.end());
+    sort(s2.begin(), s2.end());
+
+    int i = 0;
+    int j = 0;
+    int ans = 0;
+    while (i < s1.size() || j < s2.size()){
+        if (i >= s1.size()){
+            j++;
+            ans++;
+        }
+        else if (j >= s2.size()){
+            i++;
+            ans++;
+        }
+        else if (s1[i] == s2[j]){
+            i++;
+            j++;
+        }
+        else if (s1[i] < s2[j]){
+            ans++;
+            i++;
+        }
+        else if (s2[j] < s1[i]){
+            ans++;
+            j++;
+        }
+    }
+
+    cout << ans;
+
+    return 0;
+}
diff --git a/Interview Preparation Kit - CPP/05. String Manipulation/002. Alternating Characters.cpp b/Interview Preparation Kit - CPP/05. String Manipulation/002. Alternating Characters.cpp
new file mode 100644
index 00000000..e248381f
--- /dev/null
+++ b/Interview Preparation Kit - CPP/05. String Manipulation/002. Alternating Characters.cpp	
@@ -0,0 +1,33 @@
+// Problem: https://www.hackerrank.com/challenges/alternating-characters/problem
+// Score: 20
+
+
+#include <iostream>
+#include <string>
+using namespace std;
+
+
+int main(){
+    int t;
+    cin >> t;
+
+    for (int i = 0; i < t; i++) {
+        string str;
+        cin >> str;
+
+
+        char prev = '0';
+        int ans = 0;
+
+        for (char c: str){
+            if (c == prev) {
+                ans++;
+            }
+            prev = c;
+        }
+
+        cout << ans << '\n';
+    }
+
+    return 0;
+}
diff --git a/Interview Preparation Kit - CPP/05. String Manipulation/003. Sherlock and the Valid String.cpp b/Interview Preparation Kit - CPP/05. String Manipulation/003. Sherlock and the Valid String.cpp
new file mode 100644
index 00000000..2757d175
--- /dev/null
+++ b/Interview Preparation Kit - CPP/05. String Manipulation/003. Sherlock and the Valid String.cpp	
@@ -0,0 +1,50 @@
+// Problem: https://www.hackerrank.com/challenges/sherlock-and-valid-string/problem
+// Score: 35
+
+
+#include <iostream>
+#include <string>
+#include <map>
+using namespace std;
+
+
+struct default_zero_int{
+    int val = 0;
+};
+
+
+int main(){
+    string str;
+    cin >> str;
+
+    map<char, default_zero_int> arr;
+
+    for (char c: str){
+        arr[c].val++;
+    }
+
+    map<char, default_zero_int> counts;
+
+    for (auto el: arr){
+        counts[el.second.val].val++;
+    }
+
+    if (counts.size() <= 1){
+        cout << "YES";
+    }
+    else if (counts.size() > 2){
+        cout << "NO";
+    }
+    else {
+        auto el1 = *counts.begin();
+        auto el2 = *(next(counts.begin(), 1));
+
+        if (((el1.first == 1 && el1.second.val == 1) || (el2.first == 1 && el2.second.val == 1)) ||
+        ((el1.second.val == 1 || el2.second.val == 1) && (abs(el1.first - el2.first) == 1))){
+            cout << "YES";
+        }
+        else cout << "NO";
+    }
+
+    return 0;
+}
diff --git a/Interview Preparation Kit - CPP/05. String Manipulation/004. Special String Again.cpp b/Interview Preparation Kit - CPP/05. String Manipulation/004. Special String Again.cpp
new file mode 100644
index 00000000..15ca577f
--- /dev/null
+++ b/Interview Preparation Kit - CPP/05. String Manipulation/004. Special String Again.cpp	
@@ -0,0 +1,39 @@
+// Problem: https://www.hackerrank.com/challenges/special-palindrome-again/problem
+// Score: 40
+
+
+#include <iostream>
+#include <string>
+#include <vector>
+using namespace std;
+
+
+int main(){
+    int n;
+    cin >> n;
+    string str;
+    cin >> str;
+
+    vector<pair<char, int>> arr;
+    arr.push_back(make_pair(str[0], 0));
+
+    for (char c: str){
+        if (c == arr.back().first){
+            arr.back().second++;
+        }
+        else {
+            arr.push_back(make_pair(c, 1));
+        }
+    }
+
+    int ans = 0;
+    for (int i = 0; i < arr.size(); i++){
+        ans += (arr[i].second + 1) * arr[i].second / 2;
+        if ((i != 0) && (i != arr.size() - 1) && (arr[i].second == 1) && (arr[i - 1].first == arr[i + 1].first)){
+            ans += min(arr[i - 1].second, arr[i + 1].second);
+        }
+    }
+
+    cout << ans;
+    return 0;
+}
diff --git a/Interview Preparation Kit - CPP/05. String Manipulation/005. Common Child.cpp b/Interview Preparation Kit - CPP/05. String Manipulation/005. Common Child.cpp
new file mode 100644
index 00000000..732cf1ec
--- /dev/null
+++ b/Interview Preparation Kit - CPP/05. String Manipulation/005. Common Child.cpp	
@@ -0,0 +1,31 @@
+// Problem: https://www.hackerrank.com/challenges/common-child/problem
+// Score: 60
+
+
+#include <iostream>
+#include <string>
+#include <vector>
+using namespace std;
+
+
+int main(){
+    string s1, s2;
+    cin >> s1 >> s2;
+
+    vector<vector<int>> dp(s1.size() + 1, vector<int>(s2.size() + 1, 0));
+
+    for (int i = 1; i < s1.size() + 1; i++){
+            for (int j = 1; j < s2.size() + 1; j++){
+                if (s1[i - 1] == s2[j - 1]){
+                    dp[i][j] = dp[i - 1][j - 1] + 1;
+                }
+                else {
+                    dp[i][j] = max(dp[i][j - 1], dp[i - 1][j]);
+                }
+            }
+    }
+
+    cout << dp[s1.size()][s2.size()];
+
+    return 0;
+}
diff --git a/Interview Preparation Kit - CPP/05. String Manipulation/CMakeLists.txt b/Interview Preparation Kit - CPP/05. String Manipulation/CMakeLists.txt
new file mode 100644
index 00000000..e7326e12
--- /dev/null
+++ b/Interview Preparation Kit - CPP/05. String Manipulation/CMakeLists.txt	
@@ -0,0 +1,9 @@
+cmake_minimum_required (VERSION 3.8)
+
+project(string-manipulation)
+
+add_executable(task-1 001.\ Strings\ -\ Making\ Anagrams.cpp)
+add_executable(task-2 002.\ Alternating\ Characters.cpp)
+add_executable(task-3 003.\ Sherlock\ and\ the\ Valid\ String)
+add_executable(task-4 004.\ Special\ String\ Again.cpp)
+add_executable(task-5 005.\ Common\ Child.cpp)
diff --git a/Interview Preparation Kit - CPP/06. Greedy Algorithms/001. Minimum Absolute Difference in an Array.cpp b/Interview Preparation Kit - CPP/06. Greedy Algorithms/001. Minimum Absolute Difference in an Array.cpp
new file mode 100644
index 00000000..6513b09b
--- /dev/null
+++ b/Interview Preparation Kit - CPP/06. Greedy Algorithms/001. Minimum Absolute Difference in an Array.cpp	
@@ -0,0 +1,34 @@
+// Problem: https://www.hackerrank.com/challenges/minimum-absolute-difference-in-an-array/problem
+// Score: 15
+
+
+#include <iostream>
+#include <vector>
+#include <algorithm>
+using namespace std;
+
+
+int main(){
+    int n;
+    cin >> n;
+
+    vector<int> arr;
+    for (int i = 0; i < n; i++){
+        int tmp;
+        cin >> tmp;
+        arr.push_back(tmp);
+    }
+
+    sort(arr.begin(), arr.end());
+
+    int ans = abs(arr[0] - arr[1]);
+    for (int i = 1; i < arr.size(); i++){
+        if (abs(arr[i] - arr[i-1]) < ans){
+            ans = abs(arr[i] - arr[i-1]);
+        }
+    }
+
+    cout << ans;
+
+    return 0;
+}
diff --git a/Interview Preparation Kit - CPP/06. Greedy Algorithms/002. Luck Balance.cpp b/Interview Preparation Kit - CPP/06. Greedy Algorithms/002. Luck Balance.cpp
new file mode 100644
index 00000000..00b38f65
--- /dev/null
+++ b/Interview Preparation Kit - CPP/06. Greedy Algorithms/002. Luck Balance.cpp	
@@ -0,0 +1,37 @@
+// Problem: https://www.hackerrank.com/challenges/luck-balance/problem
+// Score: 20
+
+
+#include <iostream>
+#include <vector>
+#include <algorithm>
+using namespace std;
+
+
+int main(){
+
+    int n, k;
+    cin >> n >> k;
+
+    int ans = 0;
+    vector <int> arr;
+
+    for (int i = 0; i < n; i++){
+        int l, t;
+        cin >> l >> t;
+
+        if (t == 0) ans += l;
+        else arr.push_back(l);
+    }
+
+    sort(arr.rbegin(), arr.rend());
+
+    for (int i = 0; i < arr.size(); i++){
+        if (i < k) ans += arr[i];
+        else ans -= arr[i];
+    }
+
+    cout << ans;
+
+    return 0;
+}
diff --git a/Interview Preparation Kit - CPP/06. Greedy Algorithms/003. Greedy Florist.cpp b/Interview Preparation Kit - CPP/06. Greedy Algorithms/003. Greedy Florist.cpp
new file mode 100644
index 00000000..2c25f470
--- /dev/null
+++ b/Interview Preparation Kit - CPP/06. Greedy Algorithms/003. Greedy Florist.cpp	
@@ -0,0 +1,34 @@
+// Problem: https://www.hackerrank.com/challenges/greedy-florist/problem
+// Score: 35
+
+
+#include <iostream>
+#include <vector>
+#include <algorithm>
+using namespace std;
+
+
+int main(){
+    int n, k;
+    cin >> n >> k;
+    vector<int> arr;
+
+    for (int i = 0; i < n; i++){
+        int tmp;
+        cin >> tmp;
+        arr.push_back(tmp);
+    }
+
+    sort(arr.rbegin(), arr.rend());
+
+    int ans = 0;
+    int mult = 0;
+    for (int i = 0; i < n; i++){
+        if (i % k == 0) mult++;
+        ans += arr[i] * mult;
+    }
+
+    cout << ans;
+
+    return 0;
+}
diff --git a/Interview Preparation Kit - CPP/06. Greedy Algorithms/004. Max Min.cpp b/Interview Preparation Kit - CPP/06. Greedy Algorithms/004. Max Min.cpp
new file mode 100644
index 00000000..0c82e7a2
--- /dev/null
+++ b/Interview Preparation Kit - CPP/06. Greedy Algorithms/004. Max Min.cpp	
@@ -0,0 +1,32 @@
+// Problem: https://www.hackerrank.com/challenges/angry-children/problem
+// Score: 35
+
+
+#include <iostream>
+#include <vector>
+#include <algorithm>
+using namespace std;
+
+
+int main(){
+    int n, k;
+    cin >> n >> k;
+    vector<int> arr;
+
+    for (int i = 0; i < n; i++){
+        int tmp;
+        cin >> tmp;
+        arr.push_back(tmp);
+    }
+
+    sort(arr.begin(), arr.end());
+
+    int ans = arr[k - 1] - arr[0];
+    for (int i = 0; i < arr.size() - k + 1; i++){
+        int tmp = arr[k - 1 + i] - arr[i];
+        if (tmp < ans) ans = tmp;
+    }
+
+    cout << ans;
+    return 0;
+}
diff --git a/Interview Preparation Kit - CPP/06. Greedy Algorithms/CMakeLists.txt b/Interview Preparation Kit - CPP/06. Greedy Algorithms/CMakeLists.txt
new file mode 100644
index 00000000..543dabf0
--- /dev/null
+++ b/Interview Preparation Kit - CPP/06. Greedy Algorithms/CMakeLists.txt	
@@ -0,0 +1,9 @@
+cmake_minimum_required (VERSION 3.8)
+
+project(greedy-algorithms)
+
+add_executable(task-1 001.\ Minimum\ Absolute\ Difference\ in\ an\ Array.cpp)
+add_executable(task-2 002.\ Luck\ Balance.cpp)
+add_executable(task-3 003.\ Greedy\ Florist.cpp)
+add_executable(task-4 004.\ Max\ Min.cpp)
+
diff --git a/Interview Preparation Kit - CPP/07. Search/001. Hash Tables Ice Cream Parlor.cpp b/Interview Preparation Kit - CPP/07. Search/001. Hash Tables Ice Cream Parlor.cpp
new file mode 100644
index 00000000..2428e792
--- /dev/null
+++ b/Interview Preparation Kit - CPP/07. Search/001. Hash Tables Ice Cream Parlor.cpp	
@@ -0,0 +1,32 @@
+// Problem: https://www.hackerrank.com/challenges/ctci-ice-cream-parlor/problem
+// Score: 35
+
+
+#include <iostream>
+#include <map>
+using namespace std;
+
+
+int main(){
+    int t = 0;
+    cin >> t;
+
+    for (int i = 0; i < t; i++){
+        int money, n;
+        cin >> money >> n;
+        map<int, int> arr;
+
+        for (int j = 0; j < n; j++){
+            int c;
+            cin >> c;
+
+            if (arr.find(c) == arr.end()){
+                arr[money - c] = j + 1;
+            }
+            else{
+                cout << arr[c] << " " << j + 1 << '\n';
+            }
+        }
+    }
+    return 0;
+}
diff --git a/Interview Preparation Kit - CPP/07. Search/CMakeLists.txt b/Interview Preparation Kit - CPP/07. Search/CMakeLists.txt
new file mode 100644
index 00000000..6eb4d3f1
--- /dev/null
+++ b/Interview Preparation Kit - CPP/07. Search/CMakeLists.txt	
@@ -0,0 +1,6 @@
+cmake_minimum_required (VERSION 3.8)
+
+project(greedy-algorithms)
+
+add_executable(task-1 001.\ Hash\ Tables\ Ice\ Cream\ Parlor.cpp)
+
diff --git a/Interview Preparation Kit - CPP/08. Dynamic Programming/001. Max Array Sum.cpp b/Interview Preparation Kit - CPP/08. Dynamic Programming/001. Max Array Sum.cpp
new file mode 100644
index 00000000..78995425
--- /dev/null
+++ b/Interview Preparation Kit - CPP/08. Dynamic Programming/001. Max Array Sum.cpp	
@@ -0,0 +1,29 @@
+// Problem: https://www.hackerrank.com/challenges/max-array-sum/problem
+// Score: 20
+
+
+#include <iostream>
+#include <vector>
+using namespace std;
+
+
+int main(){
+    int n;
+    cin >> n;
+    vector<int> arr(n);
+
+    for (int i = 0; i < n; i++){
+        cin >> arr[i];
+    }
+
+    vector<int> dp(n);
+    dp[0] = arr[0];
+    dp[1] = max(arr[0], arr[1]);
+    for (int i = 2; i < n; i++){
+        dp[i] = max(max(dp[i-2] + arr[i], dp[i - 1]), arr[i]);
+    }
+
+    cout << dp[n - 1];
+
+    return 0;
+}
diff --git a/Interview Preparation Kit - CPP/08. Dynamic Programming/002. Abbreviation.cpp b/Interview Preparation Kit - CPP/08. Dynamic Programming/002. Abbreviation.cpp
new file mode 100644
index 00000000..958febb2
--- /dev/null
+++ b/Interview Preparation Kit - CPP/08. Dynamic Programming/002. Abbreviation.cpp	
@@ -0,0 +1,49 @@
+// Problem: https://www.hackerrank.com/challenges/abbr/problem
+// Score: 40
+
+
+#include <iostream>
+#include <string>
+#include <vector>
+using namespace std;
+
+
+int main(){
+    int q;
+    cin >> q;
+
+    for (int k = 0; k < q; k++){
+        string s1, s2;
+        cin >> s1 >> s2;
+
+        vector<vector<bool>> dp (s2.size() + 1, vector<bool> (s1.size() + 1, false));
+
+        dp[0][0] = true;
+
+        for (int i = 1; i < s2.size() + 1; i++){
+            dp[i][0] = false;
+        }
+
+        for (int i = 1; i < s1.size() + 1; i++){
+            dp[0][i] = (islower(s1[i - 1])) && (dp[0][i - 1] == true);
+        }
+
+        for (int i = 1; i < s2.size() + 1; i++){
+            for (int j = 1; j < s1.size() + 1; j++){
+                if (islower(s1[j-1])){
+                    dp[i][j] = (dp[i - 1][j - 1] && s2[i - 1] == toupper(s1[j - 1])) || dp[i][j - 1];
+                }
+                else {
+                    dp[i][j] = dp[i - 1][j - 1] && s2[i - 1] == s1[j - 1];
+                }
+
+            }
+        }
+
+        if (dp[s2.size()][s1.size()]) cout << "YES" << endl;
+        else cout << "NO" << endl;
+    }
+    return 0;
+}
+
+
diff --git a/Interview Preparation Kit - CPP/08. Dynamic Programming/003. Candies.cpp b/Interview Preparation Kit - CPP/08. Dynamic Programming/003. Candies.cpp
new file mode 100644
index 00000000..7b565558
--- /dev/null
+++ b/Interview Preparation Kit - CPP/08. Dynamic Programming/003. Candies.cpp	
@@ -0,0 +1,39 @@
+// Problem: https://www.hackerrank.com/challenges/candies/problem
+// Score: 50
+
+
+#include <iostream>
+#include <vector>
+using namespace std;
+
+
+int main(){
+    int n;
+    cin >> n;
+    vector<int> arr(n);
+    vector<int> up (n, 1);
+    vector<int> down (n, 1);
+
+    for (int i = 0; i < n; i++){
+        cin >> arr[i];
+    }
+
+    for (int i = 1; i < n; i++){
+        if (arr[i] > arr[i - 1]){
+            up[i] = up[i - 1] + 1;
+        }
+
+        if (arr[n - i - 1] > arr[n - i]){
+            down[n - i - 1] = down[n - i] + 1;
+        }
+    }
+
+    long long int ans = 0;
+    for (int i = 0; i < n; i++){
+        ans += max(up[i], down[i]);
+    }
+
+    cout << ans;
+
+    return 0;
+}
diff --git a/Interview Preparation Kit - CPP/08. Dynamic Programming/CMakeLists.txt b/Interview Preparation Kit - CPP/08. Dynamic Programming/CMakeLists.txt
new file mode 100644
index 00000000..d58cc3cd
--- /dev/null
+++ b/Interview Preparation Kit - CPP/08. Dynamic Programming/CMakeLists.txt	
@@ -0,0 +1,8 @@
+cmake_minimum_required (VERSION 3.8)
+
+project(dynamic-programming)
+
+add_executable(task-1 001.\ Max\ Array\ Sum.cpp)
+add_executable(task-2 "002. Abbreviation.cpp")
+add_executable(task-3 003.\ Candies.cpp)
+
diff --git a/Interview Preparation Kit - CPP/09. Stacks and Queues/001. Balanced Brackets.cpp b/Interview Preparation Kit - CPP/09. Stacks and Queues/001. Balanced Brackets.cpp
new file mode 100644
index 00000000..2c2734d9
--- /dev/null
+++ b/Interview Preparation Kit - CPP/09. Stacks and Queues/001. Balanced Brackets.cpp	
@@ -0,0 +1,44 @@
+// Problem: https://www.hackerrank.com/challenges/balanced-brackets/problem
+// Score: 25
+
+
+#include <iostream>
+#include <vector>
+using namespace std;
+
+
+int main(){
+    int t;
+    cin >> t;
+
+    for (int i = 0; i < t; i++){
+        string str;
+        cin >> str;
+        vector<char> brackets;
+
+        bool ans = true;
+
+        for (char c: str){
+            if (c == ')' || c == ']' || c == '}'){
+                if  ((!brackets.empty()) && (
+                        (c == ')' && brackets.back() == '(') ||
+                        (c == ']' && brackets.back() == '[') ||
+                        (c == '}' && brackets.back() == '{'))){
+                    brackets.pop_back();
+                }
+                else {
+                    ans = false;
+                    break;
+                }
+            }
+            else brackets.push_back(c);
+        }
+
+        if (ans && brackets.empty()) cout << "YES" << endl;
+        else cout << "NO" << endl;
+    }
+
+
+    return 0;
+}
+
diff --git a/Interview Preparation Kit - CPP/09. Stacks and Queues/003. Largest Rectangle.cpp b/Interview Preparation Kit - CPP/09. Stacks and Queues/003. Largest Rectangle.cpp
new file mode 100644
index 00000000..230aa6f1
--- /dev/null
+++ b/Interview Preparation Kit - CPP/09. Stacks and Queues/003. Largest Rectangle.cpp	
@@ -0,0 +1,58 @@
+// Problem: https://www.hackerrank.com/challenges/largest-rectangle/problem
+// Score: 50
+
+
+#include <iostream>
+#include <vector>
+using namespace std;
+
+
+void update_ans(long long int & ans, int i, vector<int> & positions, vector<int> & heights){
+    long long int square;
+    square = heights.back() * (i - positions.back());
+    ans = max(ans, square);
+    heights.pop_back();
+    positions.pop_back();
+}
+
+
+int main (){
+    int n;
+    cin >> n;
+
+    vector<int> arr(n);
+    for (int i = 0; i < n; i++){
+        cin >> arr[i];
+    }
+
+    vector<int> positions;
+    vector<int> heights;
+
+    long long int ans = 0;
+
+    for (int i = 0; i < n; i++){
+        if (heights.empty() || arr[i] > heights.back()){
+            heights.push_back(arr[i]);
+            positions.push_back(i);
+        }
+
+        else if (arr[i] < heights.back()){
+            int last_position = positions.back();
+
+            while (!heights.empty() && heights.back() > arr[i]){
+                last_position = positions.back();
+                update_ans(ans, i, positions, heights);
+            }
+            positions.push_back(last_position);
+            heights.push_back(arr[i]);
+        }
+    }
+
+    while (!heights.empty()){
+        update_ans(ans, n, positions, heights);
+    }
+
+    cout << ans;
+
+    return 0;
+}
diff --git a/Interview Preparation Kit - CPP/09. Stacks and Queues/CMakeLists.txt b/Interview Preparation Kit - CPP/09. Stacks and Queues/CMakeLists.txt
new file mode 100644
index 00000000..e0427d7e
--- /dev/null
+++ b/Interview Preparation Kit - CPP/09. Stacks and Queues/CMakeLists.txt	
@@ -0,0 +1,7 @@
+cmake_minimum_required (VERSION 3.8)
+
+project(stacks-and-queues)
+
+
+add_executable(task-1 "001. Balanced Brackets.cpp")
+add_executable(task-3 "003. Largest Rectangle.cpp")
diff --git a/Interview Preparation Kit - CPP/10. Graphs/003. BFS - Shortest Reach in a Graph.cpp b/Interview Preparation Kit - CPP/10. Graphs/003. BFS - Shortest Reach in a Graph.cpp
new file mode 100644
index 00000000..13b08f28
--- /dev/null
+++ b/Interview Preparation Kit - CPP/10. Graphs/003. BFS - Shortest Reach in a Graph.cpp	
@@ -0,0 +1,66 @@
+// Problem: https://www.hackerrank.com/challenges/ctci-bfs-shortest-reach/problem
+// Score: 45
+
+
+#include <iostream>
+#include <vector>
+#include <deque>
+using namespace std;
+
+
+struct node{
+    bool visited = false;
+    int path = -1;
+    vector<node*> kids;
+};
+
+
+int main(){
+    int t;
+    cin >> t;
+    for (int k = 0; k < t; k++){
+        int n, m;
+        cin >> n >> m;
+
+        vector<node*> nodes(n);
+        for (int i = 0; i < n; i++){
+            nodes[i] = new node();
+        }
+
+        for (int i = 0; i < m; i++){
+            int a, b;
+            cin >> a >> b;
+            nodes[a-1]->kids.push_back(nodes[b-1]);
+            nodes[b-1]->kids.push_back(nodes[a-1]);
+        }
+
+        int start;
+        cin >> start;
+
+        deque<node*> q;
+        q.push_back(nodes[start - 1]);
+
+        int path = 0;
+        q.front()->path = 0;
+        q.front()->visited = true;
+
+        while (!q.empty()){
+            path = q.front()->path + 6;
+
+            for (node * el: q.front()->kids){
+                if (!el->visited){
+                    el->path = path;
+                    el->visited = true;
+                    q.push_back(el);
+                }
+            }
+            q.pop_front();
+        }
+
+        for (node* el: nodes){
+            if (el->path != 0) cout << el->path << " ";
+        }
+        cout << '\n';
+    }
+    return 0;
+}
\ No newline at end of file
diff --git a/Interview Preparation Kit - CPP/10. Graphs/004. DFS - Connected Cell in a Grid.cpp b/Interview Preparation Kit - CPP/10. Graphs/004. DFS - Connected Cell in a Grid.cpp
new file mode 100644
index 00000000..c3b5ad3b
--- /dev/null
+++ b/Interview Preparation Kit - CPP/10. Graphs/004. DFS - Connected Cell in a Grid.cpp	
@@ -0,0 +1,57 @@
+// Problem: https://www.hackerrank.com/challenges/ctci-connected-cell-in-a-grid/problem
+// Score: 45
+
+
+#include <iostream>
+#include <vector>
+using namespace std;
+
+
+void count_nodes(vector<vector <int>> const & arr, vector<vector <bool>> & visited, int i, int j, int & count){
+    if (visited[i][j]) return;
+
+    visited[i][j] = true;
+    if (arr[i][j] == 0) return;
+    if (i != 0) count_nodes(arr, visited, i - 1, j, count);
+    if (i != 0 && j != 0) count_nodes(arr, visited, i - 1, j - 1, count);
+    if (i != 0 && j != arr[0].size() - 1) count_nodes(arr, visited, i - 1, j + 1, count);
+    if (j != 0) count_nodes(arr, visited, i, j - 1, count);
+    if (j != arr[0].size() - 1) count_nodes(arr, visited, i, j + 1, count);
+    if (i != arr.size() - 1) count_nodes(arr, visited, i + 1, j, count);
+    if (i != arr.size() - 1 && j != 0) count_nodes(arr, visited, i + 1, j - 1, count);
+    if (i != arr.size() - 1 && j != arr[0].size() - 1) count_nodes(arr, visited, i + 1, j + 1, count);
+    count++;
+}
+
+
+int main(){
+    int n, m;
+    cin >> n >> m;
+
+    vector<vector <int>> arr(n, vector<int>(m));
+
+    for (int i = 0; i < n; i++){
+        for (int j = 0; j < m; j++){
+            cin >> arr[i][j];
+        }
+    }
+
+    vector<vector <bool>> visited(n, vector<bool>(m, false));
+
+
+    int ans = 0;
+
+    for (int i = 0; i < n; i++){
+        for (int j = 0; j < m; j++){
+            int count = 0;
+            count_nodes(arr, visited, i, j, count);
+            if (count > ans){
+                ans = count;
+            }
+        }
+    }
+
+    cout << ans;
+
+    return 0;
+}
diff --git a/Interview Preparation Kit - CPP/10. Graphs/CMakeLists.txt b/Interview Preparation Kit - CPP/10. Graphs/CMakeLists.txt
new file mode 100644
index 00000000..d9213a22
--- /dev/null
+++ b/Interview Preparation Kit - CPP/10. Graphs/CMakeLists.txt	
@@ -0,0 +1,7 @@
+cmake_minimum_required (VERSION 3.8)
+
+project(graphs)
+
+
+add_executable(task-3 "003. BFS - Shortest Reach in a Graph.cpp")
+add_executable(task-4 "004. DFS - Connected Cell in a Grid.cpp")
diff --git a/Interview Preparation Kit - CPP/11. Trees/001. Tree - Height of a Binary Tree.cpp b/Interview Preparation Kit - CPP/11. Trees/001. Tree - Height of a Binary Tree.cpp
new file mode 100644
index 00000000..2e64ff50
--- /dev/null
+++ b/Interview Preparation Kit - CPP/11. Trees/001. Tree - Height of a Binary Tree.cpp	
@@ -0,0 +1,11 @@
+// Problem: https://www.hackerrank.com/challenges/tree-height-of-a-binary-tree/problem
+// Score: 10
+
+
+int height(Node *root) {
+    if ((root == nullptr) || (root->left == nullptr && root->right == nullptr)) {
+        return 0;
+    } else {
+        return max(height(root->left), height(root->right)) + 1;
+    }
+}
diff --git a/Interview Preparation Kit - CPP/11. Trees/CMakeLists.txt b/Interview Preparation Kit - CPP/11. Trees/CMakeLists.txt
new file mode 100644
index 00000000..962ec206
--- /dev/null
+++ b/Interview Preparation Kit - CPP/11. Trees/CMakeLists.txt	
@@ -0,0 +1,6 @@
+cmake_minimum_required (VERSION 3.8)
+
+project(trees)
+
+
+add_executable(task-1 "001. Tree - Height of a Binary Tree.cpp")
diff --git a/Interview Preparation Kit - Python/01. Warm-up Challenges/001. Sock Merchant.py b/Interview Preparation Kit - Python/01. Warm-up Challenges/001. Sock Merchant.py
new file mode 100644
index 00000000..d6dfb923
--- /dev/null
+++ b/Interview Preparation Kit - Python/01. Warm-up Challenges/001. Sock Merchant.py	
@@ -0,0 +1,18 @@
+# Problem: https://www.hackerrank.com/challenges/sock-merchant/problem
+# Score: 10
+
+
+def sock_merchant(ar):
+    list_of_socks = [0 for i in range(101)]
+    for element in ar:
+        list_of_socks[element] = list_of_socks[element] + 1
+    ans = 0
+    for sock in list_of_socks:
+        ans += sock // 2
+    return ans
+
+
+n = int(input().strip())
+ar = list(map(int, input().strip().split(' ')))
+result = sock_merchant(ar)
+print(result)
diff --git a/Interview Preparation Kit - Python/01. Warm-up Challenges/002. Counting Valleys.py b/Interview Preparation Kit - Python/01. Warm-up Challenges/002. Counting Valleys.py
new file mode 100644
index 00000000..4e7749a9
--- /dev/null
+++ b/Interview Preparation Kit - Python/01. Warm-up Challenges/002. Counting Valleys.py	
@@ -0,0 +1,21 @@
+# Problem: https://www.hackerrank.com/challenges/counting-valleys/problem
+#  Score: 15
+
+
+def counting_valleys(n, s):
+    current_level = 0
+    count = 0
+    for i in range(n):
+        if s[i] == 'U':
+            current_level += 1
+        elif s[i] == 'D':
+            current_level -= 1
+            if current_level == -1:
+                count += 1
+    return count
+
+
+n = int(input().strip())
+s = input().strip()
+result = counting_valleys(n, s)
+print(result)
diff --git a/Interview Preparation Kit - Python/01. Warm-up Challenges/003. Jumping on the Clouds.py b/Interview Preparation Kit - Python/01. Warm-up Challenges/003. Jumping on the Clouds.py
new file mode 100644
index 00000000..bc967cda
--- /dev/null
+++ b/Interview Preparation Kit - Python/01. Warm-up Challenges/003. Jumping on the Clouds.py	
@@ -0,0 +1,17 @@
+# Problem: https://www.hackerrank.com/challenges/jumping-on-the-clouds/problem
+#  Score: 20
+
+
+def jumping_on_clouds(n, c):
+    c.append(0)
+    ans = 0
+    position = 0
+    while position < n-1:
+        position += (c[position+2] == 0) + 1
+        ans += 1
+    return ans
+
+
+n = int(input())
+c = list(map(int, input().rstrip().split()))
+print(jumping_on_clouds(n, c))
diff --git a/Interview Preparation Kit - Python/01. Warm-up Challenges/004. Repeated String.py b/Interview Preparation Kit - Python/01. Warm-up Challenges/004. Repeated String.py
new file mode 100644
index 00000000..18a0f6c6
--- /dev/null
+++ b/Interview Preparation Kit - Python/01. Warm-up Challenges/004. Repeated String.py	
@@ -0,0 +1,11 @@
+# Problem: https://www.hackerrank.com/challenges/repeated-string/problem
+# Score: 20
+
+
+def repeated_string(s, n):
+    return n // len(s) * s.count('a') + s[0: n % len(s)].count('a')
+
+
+s = input()
+n = int(input())
+print(repeated_string(s, n))
diff --git a/Interview Preparation Kit - Python/02. Arrays/001. Arrays - Left Rotation.py b/Interview Preparation Kit - Python/02. Arrays/001. Arrays - Left Rotation.py
new file mode 100644
index 00000000..88e69778
--- /dev/null
+++ b/Interview Preparation Kit - Python/02. Arrays/001. Arrays - Left Rotation.py	
@@ -0,0 +1,12 @@
+# Problem: https://www.hackerrank.com/challenges/ctci-array-left-rotation/problem
+#  Score: 20
+
+
+def array_left_rotation(a, k):
+    result = a[k:] + a[:k]
+    return result
+
+
+n, k = map(int, input().strip().split(' '))
+a = list(map(int, input().strip().split(' ')))
+print(*array_left_rotation(a, k))
diff --git a/Interview Preparation Kit - Python/02. Arrays/002. 2D Array - DS.py b/Interview Preparation Kit - Python/02. Arrays/002. 2D Array - DS.py
new file mode 100644
index 00000000..1304e93b
--- /dev/null
+++ b/Interview Preparation Kit - Python/02. Arrays/002. 2D Array - DS.py	
@@ -0,0 +1,17 @@
+# Problem: https://www.hackerrank.com/challenges/2d-array/problem
+#  Score: 15
+
+
+def hourglasses(arr, i, j):
+    return sum(arr[i][j:j+3]) + arr[i+1][j+1] + sum(arr[i+2][j:j+3])
+
+
+arr = []
+for i in range(6):
+    arr.append(list(map(int, input().split())))
+
+ans = hourglasses(arr, 0, 0)
+for i in range(4):
+    for j in range(4):
+        ans = max(ans, hourglasses(arr, i, j))
+print(ans)
diff --git a/Interview Preparation Kit - Python/02. Arrays/003. New Year Chaos.py b/Interview Preparation Kit - Python/02. Arrays/003. New Year Chaos.py
new file mode 100644
index 00000000..25d8cbdb
--- /dev/null
+++ b/Interview Preparation Kit - Python/02. Arrays/003. New Year Chaos.py	
@@ -0,0 +1,20 @@
+# Problem: https://www.hackerrank.com/challenges/new-year-chaos/problem
+#  Score: 40
+
+
+t = int(input())
+for test in range(t):
+    n = int(input())
+    arr = list(map(int, input().split()))
+    count = 0
+
+    for i in range(2):
+        for j in range(len(arr) - 1, 0, -1):
+            if arr[j] < arr[j-1]:
+                arr[j], arr[j-1] = arr[j-1], arr[j]
+                count += 1
+
+    if arr == sorted(arr):
+        print(count)
+    else:
+        print('Too chaotic')
diff --git a/Interview Preparation Kit - Python/02. Arrays/004. Minimum Swaps 2.py b/Interview Preparation Kit - Python/02. Arrays/004. Minimum Swaps 2.py
new file mode 100644
index 00000000..39f7049f
--- /dev/null
+++ b/Interview Preparation Kit - Python/02. Arrays/004. Minimum Swaps 2.py	
@@ -0,0 +1,17 @@
+# Problem: https://www.hackerrank.com/challenges/minimum-swaps-2/problem
+# Score: 40
+
+
+n = int(input())
+arr = list(map(int, input().split()))
+count = 0
+
+i = 0
+while i < len(arr):
+    if arr[i] != i + 1:
+        arr[arr[i] - 1], arr[i] = arr[i], arr[arr[i] - 1]
+        count += 1
+    else:
+        i += 1
+
+print(count)
diff --git a/Interview Preparation Kit - Python/02. Arrays/005. Array Manipulation.py b/Interview Preparation Kit - Python/02. Arrays/005. Array Manipulation.py
new file mode 100644
index 00000000..24ebe546
--- /dev/null
+++ b/Interview Preparation Kit - Python/02. Arrays/005. Array Manipulation.py	
@@ -0,0 +1,21 @@
+# Problem: https://www.hackerrank.com/challenges/crush/problem
+#  Score: 60
+
+
+n, queries = map(int, input().split())
+
+arr = [0 for i in range(n+2)]
+
+for i in range(queries):
+    start, finish, k = map(int, input().split())
+    arr[start - 1] += k
+    arr[finish] -= k
+
+ans = 0
+current = 0
+for i in arr:
+    current += i
+    if current > ans:
+        ans = current
+
+print(ans)
diff --git a/Interview Preparation Kit - Python/03. Dictionaries and Hashmaps/001. Hash Tables - Ransom Note.py b/Interview Preparation Kit - Python/03. Dictionaries and Hashmaps/001. Hash Tables - Ransom Note.py
new file mode 100644
index 00000000..4ce33742
--- /dev/null
+++ b/Interview Preparation Kit - Python/03. Dictionaries and Hashmaps/001. Hash Tables - Ransom Note.py	
@@ -0,0 +1,18 @@
+# Problem: https://www.hackerrank.com/challenges/ctci-ransom-note/problem
+#  Score: 25
+
+
+from collections import Counter
+
+
+def checkMagazine(magazine, note):
+    if Counter(note) - Counter(magazine) == {}:
+        return 'Yes'
+    else:
+        return 'No'
+
+
+m, n = map(int, input().split())
+magazine = list(input().split())
+note = list(input().split())
+print(checkMagazine(magazine, note))
diff --git a/Interview Preparation Kit - Python/03. Dictionaries and Hashmaps/002. Two Strings.py b/Interview Preparation Kit - Python/03. Dictionaries and Hashmaps/002. Two Strings.py
new file mode 100644
index 00000000..d295a539
--- /dev/null
+++ b/Interview Preparation Kit - Python/03. Dictionaries and Hashmaps/002. Two Strings.py	
@@ -0,0 +1,11 @@
+# Problem: https://www.hackerrank.com/challenges/two-strings/problem
+#  Score: 25
+
+
+for i in range(int(input())):
+    str1 = set(input())
+    str2 = set(input())
+    if str1 & str2 != set():
+        print('YES')
+    else:
+        print('NO')
diff --git a/Interview Preparation Kit - Python/03. Dictionaries and Hashmaps/003. Count Triplets.py b/Interview Preparation Kit - Python/03. Dictionaries and Hashmaps/003. Count Triplets.py
new file mode 100644
index 00000000..f3c30d24
--- /dev/null
+++ b/Interview Preparation Kit - Python/03. Dictionaries and Hashmaps/003. Count Triplets.py	
@@ -0,0 +1,21 @@
+# Problem: https://www.hackerrank.com/challenges/count-triplets-1/problem
+#  Score: 25
+
+
+from collections import defaultdict
+
+
+def count_triplets(arr, r):
+    arr2 = defaultdict(int)
+    arr3 = defaultdict(int)
+    count = 0
+    for i in arr:
+        count += arr3[i]
+        arr3[i*r] += arr2[i]
+        arr2[i*r] += 1
+    return count
+
+
+n, r = map(int, input().split())
+arr = list(map(int, input().split()))
+print(count_triplets(arr, r))
diff --git a/Interview Preparation Kit - Python/03. Dictionaries and Hashmaps/004. Frequency Queries.py b/Interview Preparation Kit - Python/03. Dictionaries and Hashmaps/004. Frequency Queries.py
new file mode 100644
index 00000000..b2621d83
--- /dev/null
+++ b/Interview Preparation Kit - Python/03. Dictionaries and Hashmaps/004. Frequency Queries.py	
@@ -0,0 +1,25 @@
+# Problem: https://www.hackerrank.com/challenges/frequency-queries/problem
+#  Score: 40
+
+
+from collections import defaultdict
+
+
+arr = defaultdict(int)
+frequencies = defaultdict(int)
+result = []
+for i in range(int(input())):
+    command, value = map(int, input().split())
+    if command == 1:
+        arr[value] += 1
+        frequencies[arr[value]] += 1
+        frequencies[arr[value] - 1] -= 1
+    if command == 2 and arr[value] != 0:
+        arr[value] -= 1
+        frequencies[arr[value]] += 1
+        frequencies[arr[value] + 1] -= 1
+    if command == 3:
+        result.append(1 if frequencies[value] > 0 else 0)
+
+for i in result:
+    print(i)
diff --git a/Interview Preparation Kit - Python/03. Dictionaries and Hashmaps/005. Sherlock and Anagrams.py b/Interview Preparation Kit - Python/03. Dictionaries and Hashmaps/005. Sherlock and Anagrams.py
new file mode 100644
index 00000000..0ee173c4
--- /dev/null
+++ b/Interview Preparation Kit - Python/03. Dictionaries and Hashmaps/005. Sherlock and Anagrams.py	
@@ -0,0 +1,20 @@
+# Problem: https://www.hackerrank.com/challenges/sherlock-and-anagrams/problem
+#  Score: 50
+
+
+from collections import defaultdict
+
+
+for t in range(int(input())):
+    s = input()
+    substrings = defaultdict(int)
+
+    for i in range(1, len(s)):
+        for j in range(len(s) - i + 1):
+            substrings[''.join(sorted(s[j:j+i]))] += 1
+
+    ans = 0
+    for key, value in substrings.items():
+        ans += value*(value-1) // 2
+
+    print(ans)
diff --git a/Interview Preparation Kit - Python/04. Sorting/001. Sorting - Bubble Sort.py b/Interview Preparation Kit - Python/04. Sorting/001. Sorting - Bubble Sort.py
new file mode 100644
index 00000000..375d4e9d
--- /dev/null
+++ b/Interview Preparation Kit - Python/04. Sorting/001. Sorting - Bubble Sort.py	
@@ -0,0 +1,18 @@
+# Problem: https://www.hackerrank.com/challenges/ctci-bubble-sort/problem
+#  Score: 30
+
+
+n = int(input())
+a = list(map(int, input().split()))
+
+count = 0
+
+for i in range(n):
+    for j in range(n-1):
+        if a[j] > a[j+1]:
+            a[j], a[j+1] = a[j+1], a[j]
+            count += 1
+
+print('Array is sorted in', count, 'swaps.')
+print('First Element:', a[0])
+print('Last Element:', a[-1])
diff --git a/Interview Preparation Kit - Python/04. Sorting/002. Mark and Toys.py b/Interview Preparation Kit - Python/04. Sorting/002. Mark and Toys.py
new file mode 100644
index 00000000..996397da
--- /dev/null
+++ b/Interview Preparation Kit - Python/04. Sorting/002. Mark and Toys.py	
@@ -0,0 +1,16 @@
+# Problem: https://www.hackerrank.com/challenges/mark-and-toys/problem
+#  Score: 35
+
+
+n, k = map(int, input().split())
+prices = sorted(list(map(int, input().split())))
+
+count = 0
+total_sum = 0
+for i in prices:
+    total_sum += i
+    if total_sum > k:
+        break
+    else:
+        count += 1
+print(count)
diff --git a/Interview Preparation Kit - Python/07. Search/001. Hash Tables - Ice Cream Parlor.py b/Interview Preparation Kit - Python/07. Search/001. Hash Tables - Ice Cream Parlor.py
new file mode 100644
index 00000000..73e541a9
--- /dev/null
+++ b/Interview Preparation Kit - Python/07. Search/001. Hash Tables - Ice Cream Parlor.py	
@@ -0,0 +1,16 @@
+# Problem: https://www.hackerrank.com/challenges/ctci-ice-cream-parlor/problem
+#  Score: 35
+
+
+t = int(input())
+for i in range(t):
+    money = int(input())
+    n = int(input())
+    arr = list(map(int, input().split()))
+
+    saved_values = {}
+    for counter, value in enumerate(arr):
+        if money-value in saved_values:
+            print(saved_values[money-value] + 1, counter + 1)
+        elif value not in saved_values:
+            saved_values[value] = counter
diff --git a/Interview Preparation Kit - Python/07. Search/002. Minimum Time Required.py b/Interview Preparation Kit - Python/07. Search/002. Minimum Time Required.py
new file mode 100644
index 00000000..c97992a0
--- /dev/null
+++ b/Interview Preparation Kit - Python/07. Search/002. Minimum Time Required.py	
@@ -0,0 +1,22 @@
+# Problem: https://www.hackerrank.com/challenges/minimum-time-required/problem
+#  Score: 35
+
+
+import math
+
+
+def minimum_time(goal, machines):
+    min_days = math.ceil(goal / (len(machines) / min(machines)))
+    max_days = math.ceil(goal / (len(machines) / max(machines)))
+    while min_days < max_days:
+        day = (min_days + max_days) // 2
+        if sum(day // i for i in machines) >= goal:
+            max_days = day
+        else:
+            min_days = day + 1
+    return min_days
+
+
+n, goal = map(int, input().split())
+machines = list(map(int, input().split()))
+print(minimum_time(goal, machines))
diff --git a/Interview Preparation Kit - Python/07. Search/003. Triple sum.py b/Interview Preparation Kit - Python/07. Search/003. Triple sum.py
new file mode 100644
index 00000000..e222a5b2
--- /dev/null
+++ b/Interview Preparation Kit - Python/07. Search/003. Triple sum.py	
@@ -0,0 +1,26 @@
+# Problem: https://www.hackerrank.com/challenges/triple-sum/problem
+#  Score: 40
+
+
+def binary_search_last(arr, el, low, high):
+    if low + 1 >= high:
+        if arr[low] > el:
+            return 0
+        else:
+            return low + 1
+    middle = (low + high) // 2
+    if arr[middle] > el:
+        return binary_search_last(arr, el, low, middle)
+    else:
+        return binary_search_last(arr, el, middle, high)
+
+
+len_a, len_b, len_c = map(int, input().split())
+a = sorted(set(map(int, input().split())))
+b = sorted(list(set(map(int, input().split()))))
+c = sorted(list(set(map(int, input().split()))))
+
+ans = 0
+for i in set(b):
+    ans += binary_search_last(a, i, 0, len(a)) * binary_search_last(c, i, 0, len(c))
+print(ans)
diff --git a/Interview Preparation Kit - Python/08. Dynamic Programming/001. Max Array Sum.py b/Interview Preparation Kit - Python/08. Dynamic Programming/001. Max Array Sum.py
new file mode 100644
index 00000000..1912a746
--- /dev/null
+++ b/Interview Preparation Kit - Python/08. Dynamic Programming/001. Max Array Sum.py	
@@ -0,0 +1,18 @@
+# Problem: https://www.hackerrank.com/challenges/max-array-sum/problem
+#  Score: 20
+
+
+def max_subset_sum(arr):
+    dp = list()
+    dp.append(arr[0])
+    dp.append(max(arr[:2]))
+    ans = dp[-1]
+    for i in arr[2:]:
+        dp.append(max(i, dp[-2] + i, ans))
+        ans = max(ans, dp[-1])
+    return ans
+
+
+n = int(input())
+arr = list(map(int, input().split()))
+print(max_subset_sum(arr))