What is NeetCode 150?

Neetcode 150 is a curated list of 150 LeetCode problems designed to cover all topics in data structures. It is an invaluable resource to study for LeetCode-style interviews you might enounter at FAANG and other big tech companies. There are several categories of questions and inside each category are easy, medium, and hard questions.

Creator's original repository and website.

Below is a list of my solutions for all the problems in C++ and Python.

To contribute, see here.

Arrays & Hashing

LeetCode ID	Difficulty	Problem	Solution
217	Easy	Contains Duplicate	C++ • Python
242	Easy	Valid Anagram	C++ • Python
1	Easy	Two Sum	C++ • Python
49	Medium	Group Anagrams	C++ • Python
347	Medium	Top K Frequent Elements	C++ • Python
238	Medium	Product of Array Except Self	C++ • Python
36	Medium	Valid Sudoku	C++ • Python
271	Medium	Encode and Decode Strings	C++ • Python
128	Medium	Longest Consecutive Sequence	C++ • Python

Two Pointers

LeetCode ID	Difficulty	Problem	Solution
125	Easy	Valid Palindrome	C++ • Python
167	Medium	Two Sum II	C++ • Python
15	Medium	3Sum	C++ • Python
11	Medium	Container with Most Water	C++ • Python
42	Hard	Trapping Rain Water	C++ • Python

Sliding Window

LeetCode ID	Difficulty	Problem	Solution
121	Easy	Best Time to Buy & Sell Stock	C++ • Python
3	Medium	Longest Substring Without Repeating Characters	C++ • Python
424	Medium	Longest Repeating Character Replacement	C++ • Python
567	Medium	Permutation in String	C++ • Python
76	Hard	Minimum Window Substring	C++ • Python
239	Hard	Sliding Window Maximum	C++ • Python

Stack

LeetCode ID	Difficulty	Problem	Solution
20	Easy	Valid Parentheses	C++ • Python
155	Medium	Min Stack	C++ • Python
150	Medium	Evaluate Reverse Polish Notation	C++ • Python
22	Medium	Generate Parentheses	C++ • Python
739	Medium	Daily Temperatures	C++ • Python
853	Medium	Car Fleet	C++ • Python
84	Hard	Largest Rectangle in Histogram	C++ • Python

Binary Search

LeetCode ID	Difficulty	Problem	Solution
704	Easy	Binary Search	C++ • Python
74	Medium	Search a 2D Matrix	C++ • Python
875	Medium	Koko Eating Bananas	C++ • Python
33	Medium	Search in Rotated Sorted Array	C++ • Python
153	Medium	Find Minimum in Rotated Sorted Array	C++ • Python
981	Medium	Time Based Key-Value Store	C++ • Python
4	Hard	Median of Two Sorted Arrays	C++ • Python

Linked List

LeetCode ID	Difficulty	Problem	Solution
206	Easy	Reverse Linked List	C++ • Python
21	Easy	Merge Two Sorted Lists	C++ • Python
143	Medium	Reorder List	C++ • Python
19	Medium	Remove Nth Node From End of List	C++ • Python
141	Easy	Copy List with Random Pointer	C++ • Python
2	Medium	Add Two Numbers	C++ • Python
141	Easy	Linked List Cycle	C++ • Python
287	Medium	Find the Duplicate Number	C++ • Python
146	Medium	LRU Cache	C++ • Python
23	Hard	Merge k Sorted Lists	C++ • Python
25	Hard	Reverse Nodes in k-Group	C++ • Python

Trees

LeetCode ID	Difficulty	Problem	Solution
226	Easy	Invert Binary Tree	C++ • Python
104	Easy	Maximum Depth of Binary Tree	C++ • Python
543	Easy	Diameter of Binary Tree	C++ • Python
110	Easy	Balanced Binary Tree	C++ • Python
100	Easy	Same Tree	C++ • Python
572	Easy	Subtree Of Another Tree	C++ • Python
235	Medium	Lowest Common Ancestor Of A Binary Search Tree	C++ • Python
102	Medium	Binary Tree Level Order Traversal	C++ • Python
199	Medium	Binary Tree Right Side View	C++ • Python
1448	Medium	Count Good Nodes in Binary Tree	C++ • Python
98	Medium	Validate Binary Search Tree	C++ • Python
230	Medium	Kth Smallest Element in a BST	C++ • Python
105	Medium	Construct Binary Tree from Preorder and Inorder Traversal	C++ • Python
124	Hard	Binary Tree Maximum Path Sum	C++ • Python
297	Hard	Serialize and Deserialize Binary Tree	C++ • Python

Tries

LeetCode ID	Difficulty	Problem	Solution
208	Medium	Implement Trie (Prefix Tree)	C++ • Python
211	Medium	Design Add and Search Words Data Structure	C++ • Python
212	Hard	Word Search II	C++ • Python

Heap / Priority Queue

LeetCode ID	Difficulty	Problem	Solution
703	Easy	Kth Largest Element in a Stream	C++ • Python
1046	Easy	Last Stone Weight	C++ • Python
973	Medium	K Closest Points to Origin	C++ • Python
215	Medium	Kth Largest Element in an Array	C++ • Python
621	Medium	Task Scheduler	C++ • Python
355	Medium	Design Twitter	C++ • Python
295	Hard	Find Median from Data Stream	C++ • Python

Backtracking

LeetCode ID	Difficulty	Problem	Solution
78	Medium	Subsets	C++ • Python
39	Medium	Combination Sum	C++ • Python
46	Medium	Permutations	C++ • Python
90	Medium	Subsets II	C++ • Python
40	Medium	Combination Sum II	C++ • Python
79	Medium	Word Search	C++ • Python
131	Medium	Palindrome Partitioning	C++ • Python
17	Medium	Letter Combinations of a Phone Number	C++ • Python
51	Hard	N-Queens	C++ • Python

Graphs

LeetCode ID	Difficulty	Problem	Solution
200	Medium	Number of Islands	C++ • Python
133	Medium	Clone Graph	C++ • Python
695	Medium	Max Area of Island	C++ • Python
417	Medium	Pacific Atlantic Water Flow	C++ • Python
130	Medium	Surrounded Regions	C++ • Python
994	Medium	Rotting Oranges	C++ • Python
286	Medium	Walls and Gates	C++ • Python
207	Medium	Course Schedule	C++ • Python
210	Medium	Course Schedule II	C++ • Python
684	Medium	Redundant Connection	C++ • Python
323	Medium	Number of Connected Components In An Undirected Graph	C++ • Python
261	Medium	Graph Valid Tree	C++ • Python
127	Hard	Word Ladder	C++ • Python

Advanced Graphs

LeetCode ID	Difficulty	Problem	Solution
332	Hard	Reconstruct Itinerary	C++ • Python
1584	Medium	Min Cost to Connect All Points	C++ • Python
743	Medium	Network Delay Time	C++ • Python
778	Hard	Swim in Rising Water	C++ • Python
269	Hard	Alien Dictionary	C++ • Python
787	Medium	Cheapest Flights Within K Stops	C++ • Python

1-D Dynamic Programming

LeetCode ID	Difficulty	Problem	Solution
70	Easy	Climbing Stairs	C++ • Python
746	Easy	Min Cost Climbing Stairs	C++ • Python
198	Medium	House Robber	C++ • Python
213	Medium	House Robber II	C++ • Python
5	Medium	Longest Palindromic Substring	C++ • Python
647	Medium	Palindromic Substrings	C++ • Python
91	Medium	Decode Ways	C++ • Python
322	Medium	Coin Change	C++ • Python
152	Medium	Maximum Product Subarray	C++ • Python
139	Medium	Word Break	C++ • Python
300	Medium	Longest Increasing Subsequence	C++ • Python
416	Medium	Partition Equal Subset Sum	C++ • Python

2-D Dynamic Programing

LeetCode ID	Difficulty	Problem	Solution
62	Medium	Unique Paths	C++ • Python
1143	Medium	Longest Common Subsequence	C++ • Python
309	Medium	Best Time to Buy and Sell Stock with Cooldown	C++ • Python
518	Medium	Coin Change II	C++ • Python
494	Medium	Target Sum	C++ • Python
97	Medium	Interleaving String	C++ • Python
329	Hard	Longest Increasing Path in a Matrix	C++ • Python
115	Hard	Distinct Subsequences	C++ • Python
72	Hard	Edit Distance	C++ • Python
312	Hard	Burst Balloons	C++ • Python
10	Hard	Regular Expression Matching	C++ • Python

Greedy

LeetCode ID	Difficulty	Problem	Solution
53	Medium	Maximum Subarray	C++ • Python
55	Medium	Jump Game	C++ • Python
45	Medium	Jump Game II	C++ • Python
134	Medium	Gas Station	C++ • Python
846	Medium	Hand of Straights	C++ • Python
1899	Medium	Merge Triplets to Form Target Triplet	C++ • Python
763	Medium	Partition Labels	C++ • Python
678	Medium	Valid Parenthesis String	C++ • Python

Intervals

LeetCode ID	Difficulty	Problem	Solution
57	Medium	Insert Interval	C++ • Python
56	Medium	Merge Intervals	C++ • Python
435	Medium	Non-overlapping Intervals	C++ • Python
252	Easy	Meeting Rooms	C++ • Python
253	Medium	Meeting Rooms II	C++ • Python
1851	Hard	Minimum Interval to Include Each Query	C++ • Python

Math & Geometry

LeetCode ID	Difficulty	Problem	Solution
48	Medium	Rotate Image	C++ • Python
54	Medium	Spiral Matrix	C++ • Python
73	Medium	Set Matrix Zeroes	C++ • Python
202	Easy	Happy Number	C++ • Python
66	Easy	Plus One	C++ • Python
50	Medium	Pow(x, n)	C++ • Python
43	Medium	Multiply Strings	C++ • Python
2013	Medium	Detect Squares	C++ • Python

Bit Manipulation

LeetCode ID	Difficulty	Problem	Solution
136	Easy	Single Number	C++ • Python
191	Easy	Number of 1 Bits	C++ • Python
338	Easy	Counting Bits	C++ • Python
190	Easy	Reverse Bits	C++ • Python
268	Easy	Missing Number	C++ • Python
371	Medium	Sum of Two Integers	C++ • Python
7	Medium	Reverse Integer	C++ • Python

Contributing

If you have a better solution, feel free to open a PR. Add a small summary of your solution with space and time complexities.

Guidelines

• Make sure your code passes all the test cases on LeetCode for the problem it solves.
• Write clean code that is easy to understand.
• Give your PR a succinct and accurate title.