DSA

One question per page — problem, approach, complexity, solution.

Arrays & Hashing

Contains Duplicate

Top K Frequent Elements

Encode and Decode Strings

Product of Array Except Self

Longest Consecutive Sequence

Two Pointers

Valid Palindrome

Two Sum II - Input Array Is Sorted

Container With Most Water

Trapping Rain Water

Sliding Window

Best Time to Buy and Sell Stock

Longest Substring Without Repeating Characters

Longest Repeating Character Replacement

Permutation in String

Minimum Window Substring

Sliding Window Maximum

Stack

Valid Parentheses

Evaluate Reverse Polish Notation

Generate Parentheses

Daily Temperatures

Largest Rectangle in Histogram

Binary Search

Search a 2D Matrix

Koko Eating Bananas

Find Minimum in Rotated Sorted Array

Search in Rotated Sorted Array

Time Based Key-Value Store

Median of Two Sorted Arrays

Linked List

Reverse Linked List

Merge Two Sorted Lists

Remove Nth Node From End of List

Copy List with Random Pointer

Add Two Numbers

Linked List Cycle

Find the Duplicate Number

Merge k Sorted Lists

Reverse Nodes in k-Group

Trees

Invert Binary Tree

Maximum Depth of Binary Tree

Diameter of Binary Tree

Balanced Binary Tree

Subtree of Another Tree

Lowest Common Ancestor of a Binary Search Tree

Binary Tree Level Order Traversal

Binary Tree Right Side View

Count Good Nodes in Binary Tree

Validate Binary Search Tree

Kth Smallest Element in a BST

Construct Binary Tree from Preorder and Inorder Traversal

Binary Tree Maximum Path Sum

Serialize and Deserialize Binary Tree

Tries

Implement Trie (Prefix Tree)

Design Add and Search Words Data Structure

Heap / Priority Queue

Kth Largest Element in a Stream

Last Stone Weight

K Closest Points to Origin

Kth Largest Element in an Array

Find Median from Data Stream

Backtracking

Combination Sum

Combination Sum II

Palindrome Partitioning

Letter Combinations of a Phone Number

Graphs

Number of Islands

Max Area of Island

Walls and Gates

Rotting Oranges

Pacific Atlantic Water Flow

Surrounded Regions

Course Schedule

Course Schedule II

Graph Valid Tree

Number of Connected Components in an Undirected Graph

Redundant Connection

Advanced Graphs

Reconstruct Itinerary

Min Cost to Connect All Points

Network Delay Time

Swim in Rising Water

Alien Dictionary

Cheapest Flights Within K Stops

1-D DP

Climbing Stairs

Min Cost Climbing Stairs

House Robber II

Longest Palindromic Substring

Palindromic Substrings

Maximum Product Subarray

Longest Increasing Subsequence

Partition Equal Subset Sum

2-D DP

Longest Common Subsequence

Best Time to Buy and Sell Stock with Cooldown

Interleaving String

Longest Increasing Path in a Matrix

Distinct Subsequences

Regular Expression Matching

Greedy

Maximum Subarray

Hand of Straights

Merge Triplets to Form Target Triplet

Partition Labels

Valid Parenthesis String

Intervals

Insert Interval

Merge Intervals

Non-overlapping Intervals

Meeting Rooms II

Minimum Interval to Include Each Query

Math & Geometry

Set Matrix Zeroes

Multiply Strings

Bit Manipulation

Number of 1 Bits

Sum of Two Integers

Reverse Integer