LeetCode Practice Solutions

This year I am commited to solve on average at least 1 leetcode question a day.(It was written in 2022)

#	LeetCode	Problem	Difficulty	Date
1	1	Two Sums	Easy	Jan 22, 22
2	3	Longest substring	Medium	Jan 13, 22
3	19	Remove Nth node from the End of List	medium	Jan 13, 22
4	35	Search Insert Problem	Easy	Jan 7, 22
5	167	Two sums 2 - Input Array is sorted	Easy	Jan 11
6	189	Rotate Array	Medium	Jan 9, 22
7	278	First Bad Version	Easy	Jan 8, 22
8	283	Move Zeroes	Easy	Jan 10, 22
9	344	Rever String	Easy	Jan 11, 22
10	557	Revese Words in a String
11	567	Permutation in string	Medium	Jan 16, 22
12	704	Binary Search	Easy	Jan 7, 22
13	705	Design HashSet	Easy	Jan 7, 22
14	733	Flood Fill	Easy	Jan 18, 22
15	876	Middle of the Linked List	Easy	Jan 12, 22
16	977	Squares of a Sorted Array	Easy	Jan 8, 22
17	2095	Delete The Middle of Node of a Linked List	Medium	Feb 5, 22

Blind 75 LeetCode Questions

Below list pertains to the list of questions called "Blind 75" which is presumably a list of most important LC questions for coding interview

Array questions

#	LeetCode	Problem	Difficulty	Dates	Tips & Tricks
1	1	Two Sums	Easy	Feb 3, 22	Using hashmap to keep track of index of values in the list. For each iteration check if the current number worked, then the diff (targe- curr num) should be in the hashmap.
2	121	Best Time to Buy and Sell Stock	Easy	Feb 5, 22	Use two moving pointer and one profit var to compare
3	217	Contains duplicate	Easy	Feb 6, 22	convert list to set and check the length
4	238	Product of Array Except Self	Medium	Feb 7, 22	Two loops in each direction, finding left and right of eachnumber
5	53	Maximum Subarray	Easy	Feb 9, 22	Kadene's Algorithm. Dynamic Programming
6	152	Maximum Product Subarray	Medium	Feb 10, 22	Kadene's Algorithm. Use 3 variable to store result, min, max
7	153	Find Minimum in Rotated Sorted Array	Medium	Feb 11, 22	Pythonic way if to use min(). Otherwise use binary search and use the fact in rotated list l[last element] < l[firs element]
8	33	Search in Rotated Sorted Array	Medium	Feb 11, 22	Either left or right to the mid point if steadily increasing. Find mid point, check weather on either side target is within that range
9	15	3 Sum	Medium	Feb 12	Have a nested loop. For each number find the difference fro inner loop with two pointers
10	11	Container With Most Water	Medium	Feb 16, 22	Haven't solved yet

Binary questions

#	LeetCode	Problem	Difficulty	Dates	Tips & Tricks
11	371	Sum of Two Integers	Medium	Feb 17, 22	use XOR for adding 1 and 0; use AND for ading 1; use << for carry bit. Do until AND returns
12	191	Number of 1 bits	Easy	Feb 21, 22	And with 1 for each bit, shift bit to right
13	338	Counting Bits	Easy	Feb 22, 22	count bits for each number in list(range(n+1))
14	268	Missing Number	Easy	Feb 23, 22	XOR with itself
15	190	Reverse Bits	Easy	Feb 24, 22	loop through 32 bits

Dynamic Programming

#	LeetCode	Problem	Difficulty	Dates	Tips & Tricks
16	70	Climbing Stair	Easy	Feb 26, 22	Either 1 or 2. The rest is based on previous two stairs
17	322	Coin Change	Medium	Feb 28, 22	Bottom up: create a list of amount+1 entries. Nested loop trough each value in amount and each coin in coins. Check is using the currecnt coins is less than existing solution is the dp list.
18	300	Longest Increasing Subsequence	Medium	March 3	backwards nested loop
19	139	Word Break	Medium	March 5	Start from the end. check if currect substring in the dict.
20	377	Combination Sum IV	Medium	Jun 3	Bottom up aproach
21	198	House Robber	Medium	Jun 6

Epic Return.

Today is Aug 7, 2023 and I am resrtarting Leetcode in 2023. Below problems are from LeetCode75 StudyPlan.

#	LeetCode	Problem	Difficulty	Dates	Tips & Tricks
1	1769	Merge Strings Alternately	Easy	Aug 7, 23
2	1071	Greatest Common Divisor of Strings	Easy	Aug 7, 23
3	1431	Kids With the Greatest Number of Candies	Easy	Aug 7, 23
4	605	Can Place Flowers	Easy	Aug 7, 23
5	345	Reverse Vowels of a String	Easy	Aug 8, 23	Could use two pointer approach or collecting vowels to stack and poping them in second loop
6	151	Reverse Words in a String	Medium	Aug 8, 23	Eaasiest solution to us python built in function such as split. Othwervise trim, reverse
7	334	Increasing Triplet Subsequence	Medium	Aug 9, 23	Two inf big numbers a,b. Loop through and compare with a and b
8	283	Move Zeroes	Easy	Aug 27, 23
9	392	Is Subsequence	Easy	Aug 27, 23
10	11	Container With Most Water	Medium	Aug 29, 23	Two pointer moving towards each other. Move the pointer that points to smaller container
11	1679	Max Number of K-Sum Pairs	Medium	Aug 29, 23	itirate and see if the the difference between current and taget has been met before. Count all such pairs.
12	643	Maximum Average Subarray	Easy	Aug 30, 23
13	1456	Maximum Number of Vowels in a Substring of Given Length	Medium	Aug 30, 23	Classic sliding window question
14	1732	Find the Highest Altitude	Easy	Aug 30, 23
15	724	Find Pivot Index	Easy	Aug 30, 23
16	2215	Find the Difference of Two Arrays	Easy	Aug 30, 23
17	1207	Unique Number of Occurrences	Easy	Aug 30, 23
18	933	Number of Recent Calls	Easy	Aug 30, 23
19	209	Reverse Linked List	Easy	Aug 30, 23
20	104	Maximum Depth of Binary Tree	Easy	Aug 30, 23
21	872	Leaf-Similar Trees	Easy	Sep 12, 23
22	700	Search in a Binary Search Tree	Easy	Sep 12, 23
23	374	Guess Number Higher or Lower	Easy	Sep 12, 23
24	1657	Determine if Two Strings Are Close	Medium	Oct 11, 23
25	2352	Equal Row and Column Pairs	Medium	Oct 11, 23
26	2390	Removing Stars From a String	Medium	Oct 18, 23
27	2390	House Robber II	Medium	Oct 18, 23
28	1493	Longest Subarray of 1's After Deleting One Element	Medium	Oct 18, 23	Sliding window. as encounter 0 and zero count exceeds 1 slide window until zero count is again 1. Return longest window
29	735	Asteroid Collision	Medium	Oct 19, 23	Stack question
30	394	Decode String	Medium	Oct 19, 23	Stack question
31	394	Dota2 Senate	Medium	Oct 19, 23	Queue question
32	394	Dota2 Senate	Medium	Oct 19, 23	Stack question
33	394	Dota2 Senate	Medium	Oct 19, 23	Stack question
34	394	Dota2 Senate	Medium	Oct 19, 23	Stack question
35	2095	Delete the Middle Node of a Linked List	Medium	Oct 19, 23	Linked List
36	328	Odd Even Linked List	Medium	Oct 19, 23	Linked List
37	2130	Maximum Twin Sum of a Linked List	Medium	Oct 24, 23	Linked List
38	1448	Count Good Nodes in Binary Tree	Medium	Oct 25, 23	DFS
39	437	Path Sum III	Medium	Oct 27, 23	DFS
40	1372	Longest ZigZag Path in a Binary Tree	Medium	Nov 5, 23	DFS
41	1373	Lowest Common Ancestor of a Binary Tree	Medium	Nov 10, 23	DFS
42	700	Search in a Binary Search Tree	Medium	Dec 7, 23	Binary Search Tree
43	450	Delete Node in a BST	Medium	Dec 7, 23	Binary Search Tree
44	841	Keys and Rooms	Medium	Jan 11, 23	Graphs - DFS
45	547	Number of Provinces	Medium	Jan 12, 23	Graphs - DFS
46	1466	Reorder Routes to Make All Paths Lead to the City Zero	Medium	Jan 12, 23	Graphs - DFS