Merge pull request #18 from Anshika-G/master

Added longest common subsequence

data_structures/linked_lists/linked_list_implementation.cpp

@@ -0,0 +1,58 @@
+#include <iostream>
+
+using namespace std;
+
+//Declare Node 
+struct Node{
+    int num;
+    Node *next;
+};
+
+//Declare starting (Head) node
+struct Node *head=NULL;
+
+//Insert node at start
+void insertNode(int n){
+    struct Node *newNode=new Node;
+    newNode->num=n;
+    newNode->next=head;
+    head=newNode;
+}
+
+//Traverse/ display all nodes (print items)
+void display(){
+    if(head==NULL){
+        cout<<"List is empty!"<<endl;
+        return;
+    }
+    struct Node *temp=head;
+    while(temp!=NULL){
+        cout<<temp->num<<" ";
+        temp=temp->next;
+    }
+    cout<<endl;
+}
+
+//delete node from start
+void deleteItem(){
+    if(head==NULL){
+        cout<<"List is empty!"<<endl;
+        return;
+    }
+    cout<<head->num<<" is removed."<<endl;
+    head=head->next;
+}
+int main(){
+
+    display();
+    insertNode(10);
+    insertNode(20);
+    insertNode(30);
+    insertNode(40);
+    insertNode(50);
+    display();
+    deleteItem(); deleteItem(); deleteItem(); deleteItem(); deleteItem();
+    deleteItem();
+    display();
+    return 0;
+}

dynamic_programing/longest_common_subsequence/c++/longest_common_subsequence.cpp

@@ -0,0 +1,40 @@
+#include<iostream>
+#include<bits/stdc++.h>
+using namespace std;
+
+int lpsH(string s, int start, int end, int **output){
+	if(start > end){
+		return 0;
+	}
+
+	if(s.length() == 1 || start == end){
+		return 1;
+	}
+
+	if(output[start][end] > -1){
+		return output[start][end];
+	}
+	if(s[start] == s[end]){
+		output[start][end] = 2 + lpsH(s, start+1, end-1, output);
+		return output[start][end];
+	}
+	output[start][end] = max(lpsH(s, start+1, end, output), lpsH(s, start, end-1, output));
+	return output[start][end];
+}
+int lcs(string s1, string s2){
+  int n1 = s1.length();
+  int **output = new int*[n1+1];
+
+  for(int i = 0; i <= s1.length(); i++){
+    output[i] = new int[s2.length()+1];
+    for(int j = 0; j <= s2.length(); j++){
+      output[i][j] = -1;
+    }
+  }
+  return lpsH(s1, 0, s1.length()-1, output);
+}
+int main(){
+	string s1, s2;
+	cin >> s1 >> s2;
+	cout << lcs(s1, s2);
+}