LeetCode Top Interview 150

The LeetCode Top Interview 150 is a curated list of 150 LeetCode problems, designed to help candidates prepare for technical interviews, particularly at top tech companies, by focusing on essential data structures and algorithms.

150 Original & Classic Questions. Covers comprehensive interview topics. Best for 3+ months of preparation time.

How to Use This Resource

1. Solve the Problems: Attempt each problem on your own before looking at the solution.

2. Understand the Concepts: Make sure you understand the underlying data structures and algorithms used in each problem.

3. Make Notes: Keep a notebook or digital document where you jot down key insights, patterns, and techniques.

4. Watch Solutions: If you're stuck, watch video explanations or read detailed solutions to understand different approaches.

5. Have Fun: Enjoy the process of learning and problem-solving. The more you enjoy it, the more you'll learn!

Array / String

• Merge Sorted Array : Easy
• Remove Element : Easy
• Remove Duplicates from Sorted Array : Easy
• Remove Duplicates from Sorted Array II : Medium
• Majority Element : Easy
• Rotate Array : Medium
• Best Time to Buy and Sell Stock : Easy
• Best Time to Buy and Sell Stock II : Medium
• Jump Game : Medium
• Jump Game II : Medium
• H-Index : Medium
• Insert Delete GetRandom O(1) : Medium
• Product of Array Except Self : Medium
• Gas Station : Medium
• Candy : Hard
• Trapping Rain Water : Hard
• Roman to Integer : Easy
• Integer to Roman : Medium
• Length of Last Word : Easy
• Longest Common Prefix : Easy
• Reverse Words in a String : Medium
• Zigzag Conversion : Medium
• Find the Index of the First Occurrence in a String : Easy
• Text Justification : Hard

Two Pointers

• Valid Palindrome : Easy
• Is Subsequence : Easy
• Two Sum II - Input Array Is Sorted : Medium
• Container With Most Water : Medium
• 3Sum : Medium

Sliding Window

• Minimum Size Subarray Sum : Medium
• Longest Substring Without Repeating Characters : Medium
• Substring with Concatenation of All Words : Hard
• Minimum Window Substring : Hard

Matrix

• Valid Sudoku : Medium
• Spiral Matrix : Medium
• Rotate Image : Medium
• Set Matrix Zeroes : Medium
• Game of Life : Medium

Hashmap

• Ransom Note : Easy
• Isomorphic Strings : Easy
• Word Pattern : Easy
• Valid Anagram : Easy
• Group Anagrams : Medium
• Two Sum : Easy
• Happy Number : Easy
• Contains Duplicate II : Easy
• Longest Consecutive Sequence : Medium

Intervals

• Summary Ranges : Easy
• Merge Intervals : Medium
• Insert Interval : Medium
• Minimum Number of Arrows to Burst Balloons : Medium

Stack

• Valid Parentheses : Easy
• Simplify Path : Medium
• Min Stack : Medium
• Evaluate Reverse Polish Notation : Medium
• Basic Calculator : Hard

Linked List

• Linked List Cycle : Easy
• Add Two Numbers : Medium
• Merge Two Sorted Lists : Easy
• Copy List with Random Pointer : Medium
• Reverse Linked List II : Medium
• Reverse Nodes in k-Group : Hard
• Remove Nth Node From End of List : Medium
• Remove Duplicates from Sorted List II : Medium
• Rotate List : Medium
• Partition List : Medium
• LRU Cache : Medium

Binary Tree General

• Maximum Depth of Binary Tree : Easy
• Same Tree : Easy
• Invert Binary Tree : Easy
• Symmetric Tree : Easy
• Construct Binary Tree from Preorder and Inorder Traversal : Medium
• Construct Binary Tree from Inorder and Postorder Traversal : Medium
• Populating Next Right Pointers in Each Node II : Medium
• Flatten Binary Tree to Linked List : Medium
• Path Sum : Easy
• Sum Root to Leaf Numbers : Medium
• Binary Tree Maximum Path Sum : Hard
• Binary Search Tree Iterator : Medium
• Count Complete Tree Nodes : Easy
• Lowest Common Ancestor of a Binary Tree : Medium

Binary Tree BFS

• Binary Tree Right Side View : Medium
• Average of Levels in Binary Tree : Easy
• Binary Tree Level Order Traversal : Medium
• Binary Tree Zigzag Level Order Traversal : Medium

Binary Search Tree

• Minimum Absolute Difference in BST : Easy
• Kth Smallest Element in a BST : Medium
• Validate Binary Search Tree : Medium

Graph General

• Number of Islands : Medium
• Surrounded Regions : Medium
• Clone Graph : Medium
• Evaluate Division : Medium
• Course Schedule : Medium
• Course Schedule II : Medium

Graph BFS

• Snakes and Ladders : Medium
• Minimum Genetic Mutation : Medium
• Word Ladder : Hard

Trie

• Implement Trie (Prefix Tree) : Medium
• Design Add and Search Words Data Structure : Medium
• Word Search II : Hard

Backtracking

• Letter Combinations of a Phone Number : Medium
• Combinations : Medium
• Permutations : Medium
• Combination Sum : Medium
• N-Queens II : Hard
• Generate Parentheses : Medium
• Word Search : Medium

Divide & Conquer

• Convert Sorted Array to Binary Search Tree : Easy
• Sort List : Medium
• Construct Quad Tree : Medium
• Merge k Sorted Lists : Hard

Kadane's Algorithm

• Maximum Subarray : Medium
• Maximum Sum Circular Subarray : Medium

Binary Search

• Search Insert Position : Easy
• Search a 2D Matrix : Medium
• Find Peak Element : Medium
• Search in Rotated Sorted Array : Medium
• Find First and Last Position of Element in Sorted Array : Medium
• Find Minimum in Rotated Sorted Array : Medium
• Median of Two Sorted Arrays : Hard

Heap

• Kth Largest Element in an Array : Medium
• IPO : Hard
• Find K Pairs with Smallest Sums : Medium
• Find Median from Data Stream : Hard

Bit Manipulation

• Add Binary : Easy
• Reverse Bits : Easy
• Number of 1 Bits : Easy
• Single Number : Easy
• Single Number II : Medium
• Bitwise AND of Numbers Range : Medium

Math

• Palindrome Number : Easy
• Plus One : Easy
• Factorial Trailing Zeroes : Medium
• Sqrt(x) : Easy
• Pow(x, n) : Medium
• Max Points on a Line : Hard

1D DP

• Climbing Stairs : Easy
• House Robber : Medium
• Word Break : Medium
• Coin Change : Medium
• Longest Increasing Subsequence : Medium

Multidimensional DP

• Triangle : Medium
• Minimum Path Sum : Medium
• Unique Paths II : Medium
• Longest Palindromic Substring : Medium
• Interleaving String : Medium
• Edit Distance : Medium
• Best Time to Buy and Sell Stock III : Hard
• Best Time to Buy and Sell Stock IV : Hard
• Maximal Square : Medium

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