Hand-picked Top 70 LeetCode Questions

A (WIP) Comprehensive C++ Writeup By Ian Y.E. Pan

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The following curated list is ordered by topics. Clicking on the question title takes you to the corresponding LeetCode submission page. Clicking on each Answer takes you to a short markdown file explaining my thought process, and an attached C++ program that is guaranteed to be correct on the LeetCode platform.

P.s. Safely ignore the "Status". It's for my personal use.

Array

Status	Question & Submission Link	My C++ Implementation
✔	Two Sum (Easy)	Answer
✔	Best Time to Buy and Sell Stock (Easy)	Answer
✔	Contains Duplicate (Easy)	Answer
✔	Maximum Subarray (Medium)	Answer
✔	Product of Array Except Self (Medium)	Answer
✔	Maximum Product Subarray (Medium)	Answer
✔	Find Minimum in Rotated Sorted Array (Medium)	Answer
✔	Search in Rotated Sorted Array (Medium)	Answer
✔	3Sum (Medium)	Answer
✔	Container With Most Water (Medium)	Answer

String

Status	Question & Submission Link	My C++ Implementation
✔	Valid Anagram (Easy )	Answer
✔	Valid Parentheses (Easy )	Answer
✔	Valid Palindrome (Easy )	Answer
✔	Longest Substring Without Repeating Characters (Medium )	Answer
✔	Longest Repeating Character Replacement (Medium )	Answer
✔	Group Anagrams (Medium )	Answer
✔	Longest Palindromic Substring (Medium )	Answer
✔	Palindromic Substrings (Medium )	Answer
✔	Letter Combinations of a Phone Number (Medium )	Answer
✔	Minimum Window Substring (Hard )	Answer

Dynamic Programming

Status	Question & Submission Link	My C++ Implementation
✔	Climbing Stairs (Easy)	Answer
✔	House Robber (Medium)	Answer
✔	Coin Change (Medium)	Answer
✔	Longest Increasing Subsequence (Medium)	Answer
✔	Longest Common Subsequence (Medium)	Answer
✔	Word Break (Medium)	Answer
✔	Combination Sum IV (Medium)	Answer
✔	House Robber II (Medium)	Answer
✔	Decode Ways (Medium)	Answer
✔	Unique Paths (Medium)	Answer
✔	Jump Game (Medium)	Answer

Linked List

Status	Question & Submission Link	My C++ Implementation
✔	Reverse a Linked List (Easy)	Answer
✔	Detect Cycle in a Linked List (Easy)	Answer
✔	Merge Two Sorted Lists (Easy)	Answer
✔	Remove Nth Node From End Of List (Medium)	Answer
✔	Reorder List (Medium)	Answer

Interval

Status	Question & Submission Link	My C++ Implementation
✔	Merge Intervals (Medium)	Answer
✔	Non-overlapping Intervals (Medium)	Answer
✔	Insert Interval (Medium)	Answer

Matrix

Status	Question & Submission Link	My C++ Implementation
✔	Set Matrix Zeroes (Medium)	Answer
✔	Spiral Matrix (Medium)	Answer
✔	Rotate Image (Medium)	Answer
✔	Word Search (Medium)	Answer

Heap

Status	Question & Submission Link	My C++ Implementation
✔	Top K Frequent Elements (Medium)	Answer
✔	Merge K Sorted Lists (Hard)	Answer
✔	Find Median from Data Stream (Hard)	Answer

Tree

Status	Question & Submission Link	My C++ Implementation
✔	Maximum Depth of Binary Tree (Easy)	Answer
✔	Same Tree (Easy)	Answer
✔	Invert Binary Tree (Easy)	Answer
✔	Subtree of Another Tree (Easy)	Answer
✔	Lowest Common Ancestor of BST (Easy)	Answer
✔	Binary Tree Level Order Traversal (Medium)	Answer
✔	Construct Binary Tree from Preorder and Inorder Traversal (Medium)	Answer
✔	Validate Binary Search Tree (Medium)	Answer
✔	Kth Smallest Element in a BST (Medium)	Answer
✔	Implement Trie, i.e. Prefix Tree (Medium)	Answer
✔	Add and Search Word (Medium)	Answer
✔	Binary Tree Maximum Path Sum (Hard)	Answer
✔	Serialize and Deserialize Binary Tree (Hard)	Answer
❌	Word Search II (Hard)	Answer

Graph

Status	Question & Submission Link	My C++ Implementation
✔	Number of Islands (Medium)	Answer
✔	Clone Graph (Medium)	Answer
✔	Course Schedule (Medium)	Answer
✔	Pacific Atlantic Water Flow (Medium)	Answer
✔	Longest Consecutive Sequence (Hard)	Answer

Binary

Status	Question & Submission Link	My C++ Implementation
✔	Sum of Two Integers (Easy)	Answer
❌	Number of 1 Bits (Easy)	Answer
✔	Missing Number (Easy)	Answer
❌	Reverse Bits (Easy)	Answer
❌	Counting Bits (Medium)	Answer

References

Reference list by a Facebook tech lead