Leetcode Top Interview 🎯

This repository contains solutions to the Leetcode Top Interview 150 problems.

These problems are commonly asked in technical interviews and cover a wide range of topics, including data structures, algorithms, and problem-solving techniques.

Show some ❤️ by starring ⭐ this repository if you like it!

Table of Contents 📖

• What is Leetcode? 🧑‍💻
• About the Top Interview 150 Collection Questions 🏆
• Tips for Solving Problems 💡
• Repository Structure 🗂️
• How to Use This Repository 🚀
• Resources 📚

What is Leetcode? 🧑‍💻

Leetcode is a popular online platform that provides a collection of coding challenges. Software engineers and interview candidates widely use it to practice coding skills and prepare for technical interviews. Leetcode offers many problems to solve, classified by difficulty level and topic.

About the Top Interview 150 Collection 🏆

The Top Interview 150 collection on Leetcode is a curated set of 150 interview questions that top tech companies frequently ask. These questions are carefully selected to cover essential concepts and algorithms that interviewers expect candidates to be familiar with.

Id	Problem	Difficulty	Status
Array / String
1	Merge Sorted Array	Easy	✅
2	Remove Element	Easy	✅
3	Remove Duplicates from Sorted Array	Easy	✅
4	Remove Duplicates from Sorted Array II	Medium	✅
5	Majority Element	Easy	✅
6	Rotate Array	Medium	✅
7	Best Time to Buy and Sell Stock	Easy
8	Best Time to Buy and Sell Stock II	Medium
9	Jump Game	Medium
10	Jump Game II	Medium
11	H-Index	Medium
12	Insert Delete GetRandom O(1)	Medium
13	Product of Array Except Self	Medium
14	Gas Station	Medium
15	Candy	Hard
16	Trapping Rain Water	Hard
17	Roman to Integer	Easy	✅
18	Integer to Roman	Medium
19	Length of Last Word	Easy	✅
20	Longest Common Prefix	Easy	✅
21	Reverse Words in a String	Medium
22	Zigzag Conversion	Medium
23	Find the Index of the First Occurrence in a String	Easy	✅
24	Text Justification	Hard
Two Pointers
25	Valid Palindrome	Easy	✅
26	Is Subsequence	Easy	✅
27	Two Sum II - Input Array Is Sorted	Medium	✅
28	Container With Most Water	Medium	✅
29	3Sum	Medium	✅
Sliding Window
30	Minimum Size Subarray Sum	Medium
31	Longest Substring Without Repeating Characters	Medium
32	Substring with Concatenation of All Words	Hard
33	Minimum Window Substring	Hard
Matrix
34	Valid Sudoku	Medium
35	Spiral Matrix	Medium
36	Rotate Image	Medium
37	Set Matrix Zeroes	Medium
38	Game of Life	Medium
Hashmap
39	Ransom Note	Easy	✅
40	Isomorphic Strings	Easy	✅
41	Word Pattern	Easy
42	Valid Anagram	Easy	✅
43	Group Anagrams	Medium	✅
44	Two Sum	Easy	✅
45	Happy Number	Easy	✅
46	Contains Duplicate II	Easy	✅
47	Longest Consecutive Sequence	Medium	✅
Intervals
48	Summary Ranges	Easy	✅
49	Merge Intervals	Medium	✅
50	Insert Interval	Medium	✅
51	Minimum Number of Arrows to Burst Balloons	Medium	✅
Stack
52	Valid Parentheses	Easy
53	Simplify Path	Medium
54	Min Stack	Medium
55	Evaluate Reverse Polish Notation	Medium
56	Basic Calculator	Hard
Linked List
57	Linked List Cycle	Easy	✅
58	Add Two Numbers	Medium	✅
59	Merge Two Sorted Lists	Easy	✅
60	Copy List with Random Pointer	Medium
61	Reverse Linked List II	Medium
62	Reverse Nodes in k-Group	Hard
63	Remove Nth Node From End of List	Medium
64	Remove Duplicates from Sorted List II	Medium
65	Rotate List	Medium
66	Partition List	Medium
67	LRU Cache	Medium
Binary Tree General
68	Maximum Depth of Binary Tree	Easy	✅
69	Same Tree	Easy	✅
70	Invert Binary Tree	Easy	✅
71	Symmetric Tree	Easy
72	Construct Binary Tree from Preorder and Inorder Traversal	Medium
73	Construct Binary Tree from Inorder and Postorder Traversal	Medium
74	Populating Next Right Pointers in Each Node II	Medium
75	Flatten Binary Tree to Linked List	Medium
76	Path Sum	Easy	✅
77	Sum Root to Leaf Numbers	Medium	✅
78	Binary Tree Maximum Path Sum	Hard
79	Binary Search Tree Iterator	Medium
80	Count Complete Tree Nodes	Easy	✅
81	Lowest Common Ancestor of a Binary Tree	Medium
Binary Tree BFS
199	Binary Tree Right Side View	Medium	✅
83	Average of Levels in Binary Tree	Easy	✅
84	Binary Tree Level Order Traversal	Medium	✅
103	Binary Tree Zigzag Level Order Traversal	Medium	✅
Binary Search Tree
86	Minimum Absolute Difference in BST	Easy	✅
87	Kth Smallest Element in a BST	Medium	✅
98	Validate Binary Search Tree	Medium	✅
Graph General
200	Number of Islands	Medium	✅
130	Surrounded Regions	Medium	✅
91	Clone Graph	Medium
92	Evaluate Division	Medium
93	Course Schedule	Medium
94	Course Schedule II	Medium
Graph BFS
95	Snakes and Ladders	Medium
96	Minimum Genetic Mutation	Medium
97	Word Ladder	Hard
Trie
98	Implement Trie (Prefix Tree)	Medium
99	Design Add and Search Words Data Structure	Medium
100	Word Search II	Hard
Backtracking
101	Letter Combinations of a Phone Number	Medium	✅
102	Combinations	Medium	✅
103	Permutations	Medium	✅
104	Combination Sum	Medium	✅
105	N-Queens II	Hard	✅
106	Generate Parentheses	Medium	✅
107	Word Search	Medium	✅
Divide & Conquer
108	Convert Sorted Array to Binary Search Tree	Easy	✅
109	Sort List	Medium	✅
110	Construct Quad Tree	Medium	✅
111	Merge k Sorted Lists	Hard	✅
Kadane's Algorithm
112	Maximum Subarray	Medium
113	Maximum Sum Circular Subarray	Medium
Binary Search
114	Search Insert Position	Easy	✅
115	Search a 2D Matrix	Medium	✅
116	Find Peak Element	Medium	✅
117	Search in Rotated Sorted Array	Medium	✅
118	Find First and Last Position of Element in Sorted Array	Medium	✅
119	Find Minimum in Rotated Sorted Array	Medium	✅
120	Median of Two Sorted Arrays	Hard
Heap
121	Kth Largest Element in an Array	Medium	✅
122	IPO	Hard
123	Find K Pairs with Smallest Sums	Medium
124	Find Median from Data Stream	Hard
Bit Manipulation
125	Add Binary	Easy	✅
126	Reverse Bits	Easy
127	Number of 1 Bits	Easy
128	Single Number	Easy	✅
129	Single Number II	Medium
130	Bitwise AND of Numbers Range	Medium
Math
131	Palindrome Number	Easy	✅
132	Plus One	Easy	✅
133	Factorial Trailing Zeroes	Medium
134	Sqrt(x)	Easy
135	Pow(x, n)	Medium
136	Max Points on a Line	Hard
1D DP
137	Climbing Stairs	Easy	✅
138	House Robber	Medium
139	Word Break	Medium
140	Coin Change	Medium
141	Longest Increasing Subsequence	Medium
Multidimensional DP
142	Triangle	Medium
143	Minimum Path Sum	Medium
144	Unique Paths II	Medium
145	Longest Palindromic Substring	Medium
146	Interleaving String	Medium
147	Edit Distance	Medium
148	Best Time to Buy and Sell Stock III	Hard
149	Best Time to Buy and Sell Stock IV	Hard
150	Maximal Square	Medium

Repository Structure 🗂️

This repository is organized by problem number, with each problem having its own directory.

Inside each problem directory, you will find the solution file(s) along with a README file that provides a problem description, constraints, and additional notes if necessary.

How to Use This Repository 🚀

Navigate through the problem directories to explore solutions. Each directory contains the solution files, including explanations and sample input/output.

You can practice implementing your solutions and compare them with those provided.

Feel free to contribute by submitting your solutions or improvements. Open a pull request to share your contributions.

I recommend contributions for new languages, as currently, the solution is only available in C# 🐛.

Resources 📚

• Leetcode
• Top 150 Interview Questions - Leetcode
• Readme structure referred from this repository

Happy coding and good luck with your interview preparation! 🎉