Neetcode Solutions

This repository contains my solutions to problems from the Neetcode curated list of coding interview questions. I will be solving these problems primarily in Python.

Repository Structure

Each problem is stored in its own subfolder under the Problem directory. Each subfolder contains a Markdown file with the problem description, my thoughts, and the solution in Python or another language of choice.

Problems

Array and Hashing

Number	Problem	Leetcode Number/Solution	Difficulty
1	Contains Duplicate	217	Easy
2	Valid Anagram	242	Easy
3	Two Sum	1	Easy
4	Group Anagrams	49	Medium
5	Top K Frequent Elements	347	Medium
6	Product of Array Except Self	238	Medium
7	Valid Sudoku	36	Medium
8	String Encode and Decode	??1	Medium
9	Longest Consecutive Sequence	128	Medium

Two Pointers

Number	Problem	Leetcode Number/Solution	Difficulty
1	Valid Palindrome	125	Easy
2	Two Sum II - Input Array Is Sorted	167	Medium
3	3sum	15	Medium
4	Container With Most Water	15	Medium
4	Trapping Rain Water	42	Hard

Sliding Window

Number	Problem	Leetcode Number/Solution	Difficulty
1	Best Time to Buy and Sell Stock	121	Easy
2	Longest Substring Without Repeating Characters	3	Medium
3	Longest Repeating Character Replacement	424	Medium
4	Permutation In String	567	Medium
5	Minimum Window Substring	76	Hard
6	Sliding Window Maximum	239	Hard

Stack

Number	Problem	Leetcode Number/Solution	Difficulty
1	Valid Parentheses	20	Easy
2	Min Stack	155	Medium
3	Evaluate Reverse Polish Notation	150	Medium
4	Generate Parentheses	22	Medium
5	Daily Temperatures	739	Medium
6	Car Fleet	853	Medium
7	Largest Rectangle in Histogram	84	Hard

Binanry Search

Number	Problem	Leetcode Number/Solution	Difficulty
1	Binary Search	704	Easy
2	Search a 2D Matrix	74	Medium
3	Koko Eating Bananas	875	Medium
4	Find Minimum in Rotated Sorted Array	153	Medium
5	Search in Rotated Sorted Array	33	Medium
6	Time Based Key-Value Store	981	Medium
6	Time Based Key-Value Store	981	Medium
7	Median of Two Sorted Arrays	4	Hard

Linked List

Number	Problem	Leetcode Number/Solution	Difficulty
1	Reverse Linked List	206	Easy
2	Merge Two Sorted Lists	21	Easy
3	Reorder List	143	Medium
4	Remove Nth Node From End of List	19	Medium
5	Copy List with Random Pointer	138	Medium
6	Add Two Numbers	2	Medium
7	Linked List Cycle	141	Easy
8	Find the Duplicate Number	287	Medium
9	LRU Cache	146	Medium
10	Merge k Sorted Lists	23	Hard
11	Reverse Nodes in k-Group	25	Hard

Trees

Number	Problem	Leetcode Number/Solution	Difficulty
1	Invert Binary Tree	226	Easy
2	Maximum Depth of Binary Tree	104	Easy
3	Diameter of Binary Tree	543	Easy
4	Balanced Binary Tree	110	Easy
5	Same Tree	100	Easy
6	Subtree of Another Tree	572	Easy
7	Lowest Common Ancestor of a Binary Search Tree	235	Medium
8	Binary Tree Level Order Traversal	102	Medium
9	Binary Tree Right Side View	199	Medium
10	Count Good Nodes in Binary Tree	1448	Medium
11	Validate Binary Search Tree	98	Medium
12	Kth Smallest Element in a BST	230	Medium
13	Construct Binary Tree from Preorder and Inorder Traversal	105	Medium
14	Binary Tree Maximum Path Sum	124	Hard
14	Serialize and Deserialize Binary Tree	297	Hard

Heaps

Number	Problem	Leetcode Number/Solution	Difficulty
1	Kth Largest Element in a Stream	703	Easy
2	Last Stone Weight	1046	Easy
3	K Closest Points to Origin	973	Medium
4	Kth Largest Element in an Array	215	Medium
5	Task Scheduler	621	Medium
6	Design Twitter	355	Medium
7	Find Median from Data Stream	295	Hard

Backtracking

Number	Problem	Leetcode Number/Solution	Difficulty
1	Subsets	78	medium
2	Combination Sum	39	medium
3	Permutations	46	medium
4	Subsets II	90	medium
5	Combination Sum II	40	medium
6	Word Search	79	medium
7	Palindrome Partitioning	131	medium
7	Letter Combinations of a Phone Number	17	medium
8	N-Queens	51	hard

Tries

Number	Problem	Leetcode Number/Solution	Difficulty
1	Implement Trie (Prefix Tree)	208	medium
2	Design Add and Search Words Data Structure	211	medium
3	Word Search II	212	medium

Graphs

Number	Problem	Leetcode Number/Solution	Difficulty
1	Number of Islands	200	medium
2	Clone Graph	133	medium
3	Max Area of Island	695	medium
4	Max Area of Island	417	medium
5	Surrounded Regions	130	medium
6	Rotting ORanges	994	medium
7	Islands and Treasures	??2	medium
8	Course Schedule	207	medium
9	Course Schedule II	210	medium
10	Count Connected Components	??3	medium
11	Redundant Connection	684	medium
12	Graph Valid Tree	??4	medium
13	Word Ladder	127	hard

Advanced Graphs

Number	Problem	Leetcode Number/Solution	Difficulty
1	Reconstruct Itinerary	332	hard
2	Min Cost to Connect All Points	1584	medium
3	Network Delay Time	743	medium
4	Swim in Rising Water	778	hard
5	Foreign Dictionary	??5	hard
6	Cheapest Flights Within K Stops	787	hard

1-D Dynamic programming

Number	Problem	Leetcode Number/Solution	Difficulty
1	Reconstruct Itinerary	70	easy
2	Min Cost Climbing Stairs	746	easy
3	House Robber	198	medium
4	House Robber II	213	medium
5	Longest Palindromic Substring	5	medium
6	Palindromic Substrings	647	medium
7	Decode Ways	91	medium
7	Coin Change	322	medium
8	Maximum Product Subarray	152	medium
9	Word Break	139	medium
10	Longest Increasing Subsequence	300	medium
11	Partition Equal Subset Sum	416	medium

2-D Dynamic programming

Number	Problem	Leetcode Number/Solution	Difficulty
1	Unique Paths	62	medium
2	Longest Common Subsequence	1143	medium
3	Best Time to Buy And Sell Stock With Cooldown	309	medium
4	Coin Change II	518	medium
5	Target Sum	494	medium
6	Interleaving String	97	medium
7	Longest Increasing Path In a Matrix	329	hard
8	Distinct Subsequences	115	hard
9	Edit Distance	72	medium
10	Burst Balloons	312	hard
11	Regular Expression Matching	10	hard

Greedy

Number	Problem	Leetcode Number/Solution	Difficulty
1	Maximum Subarray	53	medium
2	Jump Game	55	medium
3	Jump Game II	45	medium
4	Gas Station	134	medium
5	Hand of Straights	846	medium
6	Merge Triplets to Form Target Triplet	1899	medium
7	Partition Labels	763	medium
8	Valid Parenthesis String	678	medium

Intervals

Number	Problem	Leetcode Number/Solution	Difficulty
1	Insert Interval	57	medium
2	Merge Intervals	56	medium
3	Non Overlapping Intervals	435	medium
4	Meeting Rooms	??6	easy
5	Meeting Rooms II	??7	medium
6	Minimum Interval to Include Each Query	1851	hard

Math & Geometry

Number	Problem	Leetcode Number/Solution	Difficulty
1	Rotate Image	48	medium
2	Spiral Matrix	54	medium
3	Set Matrix Zeroes	73	medium
4	Happy Number	202	easy
5	Plus One	66	easy
6	Pow(x, n)	50	medium
7	Multiply Strings	43	medium
8	Detect Squares	2013	medium

Bit Manipulation

Number	Problem	Leetcode Number/Solution	Difficulty
1	Single Number	136	easy
2	Number of 1 Bits	191	easy
3	Counting Bits	338	easy
4	Reverse Bits	190	easy
5	Missing Number	268	easy
6	Sum of Two Integers	371	medium
7	Reverse Integer	7	medium