Data Structures and Algorithms

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Course Introduction

Join the Community

How Coding Interviews Work

How to Communicate During Interviews

Time Management in Coding Interviews

How to Identify Which Pattern to Use

How to Handle Unseen Problems

JavaScript for DSA

TypeScript for DSA

Variables, I/O & Operators

Swap Two Numbers

Temperature Converter

Simple Interest and Compound Interest

Convert Seconds to Hours, Minutes, Seconds

Absolute Value Without Built-in

Quotient and Remainder of a Division

Area and Perimeter of Shapes

Conditionals & Decision Making

Positive, Negative, or Zero

Leap Year Check

Grade from Marks

Valid Triangle from Three Sides

Vowel or Consonant

Check if Three Points are Collinear

Loops & Iteration

Print Numbers from 1 to N

Multiplication Table of a Number

Sum of Even or Odd Numbers

Count Digits in an Integer

Sum of All Divisors of a Number

Pattern Printing

Right-Angled Triangle of Stars

Inverted Right-Angled Triangle

Pyramid of Stars

Inverted Pyramid

Hollow Triangle

Diamond Pattern

Floyd's Triangle

Mirror Number Pattern

Butterfly Pattern

Hourglass Pattern

Spiral Number Pattern

Number Theory

Prime Number Check

Print All Primes Up to N

Factorial of a Number

Print Fibonacci Up to N Terms

GCD of Two Numbers

LCM of Two Numbers

Perfect Number Check

Decimal to Binary

Array Warmups

Sum of All Elements

Average of Array Elements

Largest Element in an Array

Second Largest Element

Count Even and Odd Numbers

Linear Search for a Target

Reverse an Array In Place

Check if an Array is Sorted

Count Frequency of Each Element

String Warmups

Length of a String

Count Vowels and Consonants

Count Words in a Sentence

Palindrome String Check

Count Occurrence of a Character

Replace All Spaces with a Character

Toggle Case of Every Character

Find the Longest Word in a Sentence

Recursion

Sum of First N Natural Numbers (Recursive)

Factorial (Recursive)

Nth Fibonacci Number (Recursive)

Power of a Number (Recursive)

Reverse a String (Recursive)

Sum of Digits (Recursive)

Print Numbers 1 to N and N to 1 (Recursive)

Count Digits (Recursive)

GCD Using Recursion

Best, Worst, and Average Complexity

Amortized Analysis

Recurrence Relations

Complexity Drills

Complexity Quiz - EasyNew

Complexity Quiz - MediumNew

Complexity Quiz - HardNew

Modular Arithmetic

Matrix Exponentiation

Number Basics - Problems

Palindrome Number

Roman to Integer

Excel Sheet Column Title

Greatest Common Divisor of Strings

Number Properties - Problems

Count Good Numbers

Math Operations - Problems

Reverse Integer

Factorial Trailing Zeroes

Multiply Strings

Find the Duplicate Number

Geometry - Problems

Minimum Area Rectangle II

Valid Triangle Number

Minimum Area Rectangle

Max Points on a Line

Comparison-based

Linear Time

Specialized

External SortNew

Merge Sort - Problems

Count of Range Sum

Quick Sort / QuickSelect

Kth Largest Element in an Array

Find the Kth Largest Integer in the Array

Bucket Sort - Problems

Sort Characters By Frequency

Top K Frequent Words

Contains Duplicate III

Introduction to Arrays

Array Manipulation

Shuffle the Array

Remove Duplicates from Sorted Array

Remove Duplicates from Sorted Array II

Finding & Counting

Max Consecutive Ones

Third Maximum Number

Majority Element

Majority Element II

Stock Problems

Best Time to Buy and Sell Stock

Best Time to Buy and Sell Stock II

Subarrays & Subsequences

Number of Zero-Filled Subarrays

Increasing Triplet Subsequence

Advanced Techniques

Product of Array Except Self

Next Permutation

First Missing Positive

String Basics

Length of Last Word

Find the Index of the First Occurrence in a String

Palindromes

Valid Palindrome

Valid Palindrome II

Longest Palindrome

Anagrams & Patterns

Longest Common Prefix

String Transformations

Zigzag Conversion

Reverse Words in a String

One Edit Distance

Determine if Two Strings Are Close

Add Bold Tag in String

Hard String Problems

Text Justification

Introduction to Bit Manipulation

XOR Tricks

Single Number II

Single Number III

Bit Counting

Number of 1 Bits

Hamming Distance

Bit Masking

Bitwise AND of Numbers Range

Sum of Two Integers

Introduction to Hash Tables

Frequency Counting

Frequency & Counting

Maximum Number of Balloons

Number of Good Pairs

First Unique Character in a String

Find All Numbers Disappeared in an Array

Duplicate Detection

Contains Duplicate

Contains Duplicate II

Intersection of Two Arrays II

Pattern Matching

Isomorphic Strings

Group Shifted Strings

Advanced Hashing

Encode and Decode TinyURL

Reorganize String

Longest Consecutive Sequence

Number of Matching Subsequences

Number of Good Ways to Split a String

Split Array into Consecutive Subsequences

Minimum Deletions to Make Character Frequencies Unique

Introduction to Two Pointers

Opposite Direction

Squares of a Sorted Array

Merge Strings Alternately

Valid Word Abbreviation

Two Sum II - Input Array Is Sorted

Container With Most Water

Trapping Rain Water

Count Subarrays With Fixed Bounds

Same Direction

Merge Sorted Array

Backspace String Compare

Count Binary Substrings

String Compression

Boats to Save People

Longest Palindromic Substring

Introduction to Sliding Window

Fixed Size

Maximum Average Subarray I

Find All Anagrams in a String

Permutation in String

Maximum Sum of Distinct Subarrays With Length K

Maximum Number of Vowels in a Substring of Given Length

Substring with Concatenation of All Words

Dynamic Size

Longest Substring Without Repeating Characters

Longest Repeating Character Replacement

Minimum Size Subarray Sum

Max Consecutive Ones III

Count Number of Nice Subarrays

Fruit Into Baskets

Maximum Points You Can Obtain from Cards

Subarray Product Less Than K

Frequency of the Most Frequent Element

Longest Substring with At Most Two Distinct Characters

Longest Substring with At Most K Distinct Characters

Longest Substring with At Least K Repeating Characters

Minimum Window Substring

Minimum Window Subsequence

Subarrays with K Different Integers

Introduction to Prefix Sum

Basic Prefix Sum

Range Sum Query - Immutable

Running Sum of 1d Array

Find Pivot Index

Maximum Population Year

Prefix Sum + Hash Map

Subarray Sum Equals K

Subarray Sums Divisible by K

Continuous Subarray Sum

Contiguous Array

2D Prefix Sum

Range Sum Query 2D - Immutable

Increment Submatrices by One

Matrix Block Sum

Introduction to Kadane's Algorithm

Classic Kadane

Maximum Subarray

Best Sightseeing Pair

Kadane Variants

Maximum Sum Circular Subarray

Maximum Product Subarray

Longest Turbulent Subarray

Kadane with Constraints

Maximum Subarray Sum with One Deletion

Maximum Absolute Sum of Any Subarray

Introduction to Binary Search

Standard Binary Search

First Bad Version

Valid Perfect Square

Search Insert Position

Guess Number Higher or Lower

Find Smallest Letter Greater Than Target

Find First and Last Position of Element in Sorted Array

Modified Binary Search

Search in Rotated Sorted Array

Search in Rotated Sorted Array II

Find Minimum in Rotated Sorted Array

Find Peak Element

Find in Mountain Array

Binary Search on Answer

Koko Eating Bananas

Capacity To Ship Packages Within D Days

Minimum Number of Days to Make m Bouquets

Magnetic Force Between Two Balls

Split Array Largest Sum

Binary Search on Matrix

Search a 2D Matrix

Search a 2D Matrix II

Binary Search Advanced

Random Pick with Weight

Find K Closest Elements

Median of Two Sorted Arrays

Find K-th Smallest Pair Distance

Matrix Traversal

Spiral Matrix II

Diagonal Traverse

Matrix Transformation

Transpose Matrix

Set Matrix Zeroes

Introduction to Linked List

Intersection of Two Linked Lists

Remove Duplicates from Sorted List

Design Linked List

Remove Nth Node From End of List

Remove Duplicates from Sorted List II

Swap Nodes in Pairs

Copy List with Random Pointer

Add Two Numbers

Flatten a Multilevel Doubly Linked List

Delete the Middle Node of a Linked List

Odd Even Linked List

Add Two Numbers II

Delete Node in a Linked List

Insert into a Sorted Circular Linked List

Merge In Between Linked Lists

In-place Reversal

Palindrome Linked List

Reverse Linked List

Reverse Linked List II

Reverse Nodes in k-Group

Fast and Slow Pointers

Middle of the Linked List

Linked List Cycle II

Introduction to Stack

Valid Parentheses

Remove All Adjacent Duplicates In String

Maximum Nesting Depth of the Parentheses

Remove Duplicate Letters

Removing Stars From a String

Evaluate Reverse Polish Notation

Basic Calculator II

Asteroid Collision

Valid Parenthesis String

Validate Stack Sequences

Minimum Remove to Make Valid Parentheses

Exclusive Time of Functions

Basic Calculator

Longest Valid Parentheses

Monotonic Stack

Introduction to Monotonic Stack

Next Greater Element I

Final Prices With a Special Discount in a Shop

Daily Temperatures

Online Stock Span

Next Greater Element II

Buildings With an Ocean View

Remove K Digits

Maximum Width Ramp

Max Chunks To Make Sorted

Sum of Subarray Minimums

Sum of Subarray Ranges

Shortest Unsorted Continuous Subarray

Next Greater Node In Linked List

Create Maximum Number

Number of Visible People in a Queue

Largest Rectangle in Histogram

Introduction to Queue

Number of Recent Calls

Time Needed to Buy Tickets

Moving Average from Data Stream

Reveal Cards In Increasing Order

First Unique Number

Number of People Aware of a Secret

Find the Winner of the Circular Game

Monotonic Queue

Continuous Subarrays

Find the Most Competitive Subsequence

Count Partitions With Max-Min Difference at Most K

Longest Continuous Subarray With Absolute Diff Less Than or Equal to Limit

Sliding Window Maximum

Max Value of Equation

Constrained Subsequence Sum

Shortest Subarray with Sum at Least K

Recursion Fundamentals

Introduction to Backtracking

Introduction to Divide and Conquer

Recursion Basics

Merge Two Sorted Lists

Divide and Conquer Problems

Longest Nice Substring

Convert Sorted List to Binary Search Tree

Construct Quad Tree

Maximum Binary Tree

Subsets & Combinations

Combination Sum

Combination Sum II

Combination Sum III

Permutations

Letter Combinations of a Phone Number

Permutations II

Partitioning & Parsing

Generate Parentheses

Palindrome Partitioning

Restore IP Addresses

Hard Backtracking

Special Binary String

Integer to English Words

Unique Paths III

Remove Invalid Parentheses

Introduction to Binary Tree

Level Order

Maximum Depth of Binary Tree

Average of Levels in Binary Tree

Binary Tree Level Order Traversal

Binary Tree Right Side View

Binary Tree Zigzag Level Order Traversal

Populating Next Right Pointers in Each Node II

Maximum Width of Binary Tree

Binary Tree Vertical Order Traversal

Populating Next Right Pointers in Each Node

Check Completeness of a Binary Tree

Pre Order

Binary Tree Preorder Traversal

Binary Tree Paths

Convert Sorted Array to Binary Search Tree

Count Complete Tree Nodes

Sum of Left Leaves

Subtree of Another Tree

Longest Univalue Path

Maximum Difference Between Node and Ancestor

Construct Binary Tree from Preorder and Inorder Traversal

Construct Binary Tree from Inorder and Postorder Traversal

Serialize and Deserialize Binary Tree

In Order

Binary Tree Inorder Traversal

Minimum Distance Between BST Nodes

Minimum Absolute Difference in BST

Validate Binary Search Tree

Kth Smallest Element in a BST

Binary Search Tree Iterator

Balance a Binary Search Tree

Post Order

Binary Tree Postorder Traversal

Invert Binary Tree

Diameter of Binary Tree

Balanced Binary Tree

Delete Nodes And Return Forest

Lowest Common Ancestor of a Binary Tree

Find Duplicate Subtrees

Flatten Binary Tree to Linked List

Distribute Coins in Binary Tree

Count Good Nodes in Binary Tree

Sum Root to Leaf Numbers

Boundary of Binary Tree

Step-By-Step Directions From a Binary Tree Node to Another

Binary Tree Maximum Path Sum

Introduction to BST

Red Black TreeNew

Basic BST Operations

Search in a Binary Search Tree

Closest Binary Search Tree Value

Two Sum IV - Input is a BST

Range Sum of BST

BST Modification

Trim a Binary Search Tree

Insert into a Binary Search Tree

Delete Node in a BST

Recover Binary Search Tree

BST Navigation

Inorder Successor in BST

Inorder Successor in BST II

Lowest Common Ancestor of a Binary Search Tree

BST Construction

Construct Binary Search Tree from Preorder Traversal

Convert Binary Search Tree to Sorted Doubly Linked List

Largest BST Subtree

Ordered Set Applications

Stock Price Fluctuation

Introduction to Heaps

Last Stone Weight

Furthest Building You Can Reach

Single-Threaded CPU

Process Tasks Using Servers

Minimum Cost to Connect Sticks

Longest Happy String

Maximum Performance of a Team

Two Heaps

Find Median from Data Stream

Sliding Window Median

K-Way Merge

Find K Pairs with Smallest Sums

Kth Smallest Element in a Sorted Matrix

Merge k Sorted Lists

Smallest Range Covering Elements from K Lists

Top K Elements

Introduction to Top K

Kth Largest Element in a Stream

Top K Frequent Elements

K Closest Points to Origin

Introduction to Intervals

Interval Basics

Merge & Insert

Merge Intervals

Insert Interval

Remove Covered Intervals

Greedy Intervals

Non-overlapping Intervals

Minimum Number of Arrows to Burst Balloons

Maximum Number of Events That Can Be Attended

Partition Labels

Meeting Rooms

Meeting Rooms II

Meeting Scheduler

Interval List Intersections

Two Best Non-Overlapping Events

Hard Intervals

Meeting Rooms III

Employee Free Time

Introduction to Trie

Trie Implementation

Implement Trie (Prefix Tree)

Prefix & Search

Design Add and Search Words Data Structure

Search Suggestions System

Longest Word in Dictionary

Trie String Operations

Remove Sub-Folders from the Filesystem

Find the Length of the Longest Common Prefix

Words Within Two Edits of Dictionary

Trie + Bit Operations

Maximum XOR of Two Numbers in an Array

Hard Trie

Stream of Characters

Concatenated Words

Palindrome Pairs

Stack & Queue Design

Implement Queue using Stacks

Implement Stack using Queues

Design Circular Queue

Design Circular Deque

Rate Limiting & Counters

Logger Rate Limiter

Design Hit Counter

Key-Value Stores

Time Based Key-Value Store

Encode and Decode Strings

Randomized Design

Insert Delete GetRandom O(1)

History & Navigation

Design Browser History

Cache Design

Complex System Design

Design a Food Rating System

Maximum Frequency Stack

All O`one Data Structure

Design Search Autocomplete System

Design In-Memory File System

Design a Text Editor

Introduction to Greedy Algorithm

Selection Greedy

Apple Redistribution into Boxes

Jump Problems

Parentheses & String

Minimum Add to Make Parentheses Valid

Maximum Score From Removing Substrings

Scheduling

Queue Reconstruction by Height

Avoid Flood in The City

Most Profit Assigning Work

Array Greedy

Maximum Matrix Sum

Hard Greedy

Minimum Number of Refueling Stops

Minimum Cost to Hire K Workers

Set Intersection Size At Least Two

Introduction to Graphs

Depth-First Search

Breadth-First Search

Matrix Traversal

Multi-Source BFS

Cycle Detection in Undirected Graphs

Cycle Detection in Directed Graphs

Bipartite Graph Detection

A* Search AlgorithmNew

Kosaraju's AlgorithmNew

Tarjan's AlgorithmNew

DFS Problems

Number of Islands

Number of Distinct Islands

Time Needed to Inform All Employees

All Paths From Source to Target

Is Graph Bipartite?

All Nodes Distance K in Binary Tree

Employee Importance

Surrounded Regions

Pacific Atlantic Water Flow

Number of Enclaves

Making A Large Island

Critical Connections in a Network

Longest Path With Different Adjacent Characters

BFS Problems

Rotting Oranges

Snakes and Ladders

Minimum Genetic Mutation

Walls and Gates

Minimum Knight Moves

Shortest Path in Binary Matrix

Path With Maximum Minimum Value

Minimum Obstacle Removal to Reach Corner

Shortest Path in a Grid with Obstacles Elimination

Topological Sort

Introduction to Topological Sort

Course Schedule II

Find Eventual Safe States

Minimum Height Trees

Course Schedule IV

Parallel Courses

Find All Possible Recipes from Given Supplies

Alien Dictionary

Sort Items by Groups Respecting Dependencies

Union Find

Introduction to Union Find

Number of Provinces

Redundant Connection

Number of Connected Components in an Undirected Graph

Graph Valid Tree

Evaluate Division

Most Stones Removed with Same Row or Column

Number of Islands II

Minimize Malware Spread

Minimum Spanning Tree

Min Cost to Connect All Points

Connecting Cities With Minimum Cost

Optimize Water Distribution in a Village

Find Critical and Pseudo-Critical Edges in Minimum Spanning Tree

Maximize Spanning Tree Stability with Upgrades

Shortest Path

Introduction to Shortest Path

Dijkstra's AlgorithmNew

Bellman-Ford AlgorithmNew

Floyd-Warshall AlgorithmNew

Network Delay Time

Cheapest Flights Within K Stops

Path with Maximum Probability

Path With Minimum Effort

Minimum Cost to Convert String I

Minimum Cost Path with Edge Reversals

Find Minimum Time to Reach Last Room I

Swim in Rising Water

Minimum Cost to Make at Least One Valid Path in a Grid

Minimum Weighted Subgraph With the Required Paths

Eulerian Circuit

Reconstruct Itinerary

Cracking the Safe

Valid Arrangement of Pairs

Introduction to Dynamic Programming

1-D DP

Introduction to 1-D DP

Fibonacci Number

Climbing Stairs

Min Cost Climbing Stairs

House Robber II

Maximum Length of Pair Chain

Delete and Earn

Greatest Sum Divisible by Three

Number of Ways to Paint N × 3 Grid

0/1 Knapsack

Introduction to Knapsack

Partition Equal Subset Sum

Last Stone Weight II

Ones and Zeroes

Profitable Schemes

Unbounded Knapsack

Introduction to Unbounded Knapsack

Perfect Squares

Minimum Cost For Tickets

LIS

Longest Increasing Subsequence

Number of Longest Increasing Subsequence

Longest String Chain

Longest Arithmetic Subsequence

Russian Doll Envelopes

2D (Grid) DP

Introduction to 2-D DP

Pascal's Triangle

Unique Paths II

Minimum Path Sum

Count Square Submatrices with All Ones

Maximum Number of Points with Cost

Minimum Falling Path Sum

Maximum Profit in Job Scheduling

Longest Increasing Path in a Matrix

Maximal Rectangle

Painting a Grid With Three Different Colors

Minimum Cost Path with Teleportations

Optimal Account Balancing

Minimum Difficulty of a Job Schedule

Minimum Cost to Cut a Stick

String DP

Introduction to String DP

Longest Common Subsequence

Longest Palindromic Subsequence

Interleaving String

Minimum Deletions to Make String Balanced

Wildcard Matching

Distinct Subsequences

Palindrome Partitioning II

Regular Expression Matching

Strange Printer

Shortest Common Supersequence

Tree / Graph DP

Introduction to Tree/Graph DP

House Robber III

Unique Binary Search Trees II

Number of Ways to Arrive at Destination

Binary Tree Cameras

Sum of Distances in Tree

Bitmask DP

Introduction to Bitmask DP

Minimum Number of Work Sessions to Finish the Tasks

Fair Distribution of Cookies

Campus Bikes II

Partition to K Equal Sum Subsets

Shortest Path Visiting All Nodes

Digit DP

Introduction to Digit DP

Count Numbers with Unique Digits

Number of Digit One

Numbers At Most N Given Digit Set

Probability DP

Introduction to Probability DP

Knight Probability in Chessboard

State Machine DP

Introduction to State Machine DP

Best Time to Buy and Sell Stock with Cooldown

Best Time to Buy and Sell Stock with Transaction Fee

Best Time to Buy and Sell Stock III

Best Time to Buy and Sell Stock IV

String Matching

Introduction to Pattern MatchingNew

Brute Force Pattern MatchingNew

KMP AlgorithmNew

Rabin-Karp AlgorithmNew

Suffix ArraysNew

Repeated Substring Pattern

Repeated String Match

Number of Distinct Substrings in a String

Shortest Palindrome

Longest Happy Prefix

Longest Duplicate Substring

Advanced Data Structures

Fenwick Tree (Binary Indexed Tree)New

Segment TreeNew

Segment Tree with Lazy PropagationNew

Range Sum Query - Mutable

Range Sum Query 2D - Mutable

Count of Smaller Numbers After Self

Falling Squares

Block Placement Queries

Longest Balanced Subarray II

Number of Pairs Satisfying Inequality

Line Sweep

Minimum Interval to Include Each Query

The Skyline Problem

Rectangle Area II

Perfect Rectangle

Data Structures and Algorithms

Welcome

Course Introduction
Course Roadmap
Join the Community

Coding Interview Strategy

How Coding Interviews Work
How to Communicate During Interviews
Time Management in Coding Interviews
How to Identify Which Pattern to Use
How to Handle Unseen Problems

Programming Fundamentals

Java for DSA
Python for DSA
C++ for DSA
C# for DSA
Go for DSA
JavaScript for DSA
TypeScript for DSA

DSA Warmup

Big O Notation

Introduction
Best, Worst, and Average Complexity
Amortized Analysis
Recurrence Relations
Master Theorem
Complexity Quiz - Easy
Complexity Quiz - Medium
Complexity Quiz - Hard

Math Fundamentals

Logarithms
Modular Arithmetic
GCD and LCM
Prime Sieve
Combinatorics
Matrix Exponentiation
Palindrome Number
Plus One
Roman to Integer
Excel Sheet Column Title
Greatest Common Divisor of Strings
Ugly Number
Ugly Number II
Count Primes
Count Good Numbers
Reverse Integer
Factorial Trailing Zeroes
Multiply Strings
Find the Duplicate Number
Valid Square
Minimum Area Rectangle II
Valid Triangle Number
Minimum Area Rectangle
Max Points on a Line

Sorting Algorithms

Bubble Sort
Selection Sort
Insertion Sort
Shell Sort
Merge Sort
Quick Sort
Heap Sort
Counting Sort
Bucket Sort
Radix Sort
Cyclic Sort
Tim Sort
External Sort
Sort an Array
Sort List
Reverse Pairs
Count of Range Sum
Sort Colors
Kth Largest Element in an Array
Find the Kth Largest Integer in the Array
Sort Characters By Frequency
Top K Frequent Words
Maximum Gap
Contains Duplicate III

Arrays

Introduction to Arrays
Move Zeroes
Remove Element
Shuffle the Array
Remove Duplicates from Sorted Array
Remove Duplicates from Sorted Array II
Rotate Array
Max Consecutive Ones
Third Maximum Number
Missing Ranges
Majority Element
Majority Element II
Best Time to Buy and Sell Stock
Best Time to Buy and Sell Stock II
Number of Zero-Filled Subarrays
Increasing Triplet Subsequence
Product of Array Except Self
Next Permutation
First Missing Positive

Strings

Reverse String
Length of Last Word
Find the Index of the First Occurrence in a String
Valid Palindrome
Valid Palindrome II
Longest Palindrome
Valid Anagram
Rotate String
Is Subsequence
Longest Common Prefix
Zigzag Conversion
Reverse Words in a String
One Edit Distance
Count and Say
Determine if Two Strings Are Close
Add Bold Tag in String
Guess the Word
Text Justification

Bit Manipulation

Introduction to Bit Manipulation
Single Number
Missing Number
Set Mismatch
Single Number II
Single Number III
Number of 1 Bits
Counting Bits
Hamming Distance
Power of Two
Reverse Bits
Bitwise AND of Numbers Range
Sum of Two Integers

Hash Tables

Introduction to Hash Tables
Frequency Counting
Design HashMap
Maximum Number of Balloons
Number of Good Pairs
Ransom Note
First Unique Character in a String
Find All Numbers Disappeared in an Array
Contains Duplicate
Contains Duplicate II
Intersection of Two Arrays II
Isomorphic Strings
Word Pattern
Group Anagrams
Group Shifted Strings
Encode and Decode TinyURL
Reorganize String
Longest Consecutive Sequence
Number of Matching Subsequences
Number of Good Ways to Split a String
Split Array into Consecutive Subsequences
Minimum Deletions to Make Character Frequencies Unique

Two Pointers

Introduction to Two Pointers
Squares of a Sorted Array
Merge Strings Alternately
Valid Word Abbreviation
Two Sum
Two Sum II - Input Array Is Sorted
Container With Most Water
3Sum
4Sum
Trapping Rain Water
Count Subarrays With Fixed Bounds
Merge Sorted Array
Backspace String Compare
Count Binary Substrings
String Compression
Boats to Save People
Longest Palindromic Substring

Sliding Window

Introduction to Sliding Window
Maximum Average Subarray I
Find All Anagrams in a String
Permutation in String
Maximum Sum of Distinct Subarrays With Length K
Maximum Number of Vowels in a Substring of Given Length
Substring with Concatenation of All Words
Longest Substring Without Repeating Characters
Longest Repeating Character Replacement
Minimum Size Subarray Sum
Max Consecutive Ones III
Count Number of Nice Subarrays
Fruit Into Baskets
Maximum Points You Can Obtain from Cards
Subarray Product Less Than K
Frequency of the Most Frequent Element
Longest Substring with At Most Two Distinct Characters
Longest Substring with At Most K Distinct Characters
Longest Substring with At Least K Repeating Characters
Minimum Window Substring
Minimum Window Subsequence
Subarrays with K Different Integers

Prefix Sum

Introduction to Prefix Sum
Range Sum Query - Immutable
Running Sum of 1d Array
Find Pivot Index
Maximum Population Year
Subarray Sum Equals K
Subarray Sums Divisible by K
Continuous Subarray Sum
Contiguous Array
Range Addition
Range Sum Query 2D - Immutable
Increment Submatrices by One
Matrix Block Sum

Kadane's Algorithm

Introduction to Kadane's Algorithm
Maximum Subarray
Best Sightseeing Pair
Maximum Sum Circular Subarray
Maximum Product Subarray
Longest Turbulent Subarray
Maximum Subarray Sum with One Deletion
Maximum Absolute Sum of Any Subarray

Binary Search

Introduction to Binary Search
Binary Search
First Bad Version
Valid Perfect Square
Search Insert Position
Guess Number Higher or Lower
Find Smallest Letter Greater Than Target
Find First and Last Position of Element in Sorted Array
Search in Rotated Sorted Array
Search in Rotated Sorted Array II
Find Minimum in Rotated Sorted Array
Find Peak Element
Find in Mountain Array
Koko Eating Bananas
Capacity To Ship Packages Within D Days
Minimum Number of Days to Make m Bouquets
Magnetic Force Between Two Balls
Split Array Largest Sum
Search a 2D Matrix
Search a 2D Matrix II
Random Pick with Weight
Find K Closest Elements
Heaters
Median of Two Sorted Arrays
Find K-th Smallest Pair Distance

Matrix

Spiral Matrix
Spiral Matrix II
Diagonal Traverse
Valid Sudoku
Transpose Matrix
Rotate Image
Set Matrix Zeroes
Candy Crush
Game of Life

Linked List

Introduction to Linked List
Intersection of Two Linked Lists
Remove Duplicates from Sorted List
Design Linked List
Remove Nth Node From End of List
Remove Duplicates from Sorted List II
Swap Nodes in Pairs
Copy List with Random Pointer
Partition List
Rotate List
Add Two Numbers
Flatten a Multilevel Doubly Linked List
Delete the Middle Node of a Linked List
Odd Even Linked List
Reorder List
Add Two Numbers II
Delete Node in a Linked List
Insert into a Sorted Circular Linked List
Merge In Between Linked Lists
Introduction
Palindrome Linked List
Reverse Linked List
Reverse Linked List II
Reverse Nodes in k-Group
Introduction
Middle of the Linked List
Happy Number
Linked List Cycle II

Stacks

Queues

Introduction to Queue
Number of Recent Calls
Time Needed to Buy Tickets
Moving Average from Data Stream
Reveal Cards In Increasing Order
First Unique Number
Number of People Aware of a Secret
Find the Winner of the Circular Game
Continuous Subarrays
Jump Game VI
Find the Most Competitive Subsequence
Count Partitions With Max-Min Difference at Most K
Longest Continuous Subarray With Absolute Diff Less Than or Equal to Limit
Sliding Window Maximum
Max Value of Equation
Constrained Subsequence Sum
Shortest Subarray with Sum at Least K

Recursion & Backtracking

Recursion Fundamentals
Introduction to Backtracking
Introduction to Divide and Conquer
Merge Two Sorted Lists
Pow(x, n)
Decode String
Longest Nice Substring
Convert Sorted List to Binary Search Tree
Construct Quad Tree
Maximum Binary Tree
Subsets
Combination Sum
Combination Sum II
Subsets II
Combination Sum III
Combinations
Permutations
Letter Combinations of a Phone Number
Permutations II
Generate Parentheses
Palindrome Partitioning
Restore IP Addresses
N-Queens
Special Binary String
Integer to English Words
Unique Paths III
Remove Invalid Parentheses
Sudoku Solver

Binary Tree

Introduction to Binary Tree
Maximum Depth of Binary Tree
Average of Levels in Binary Tree
Binary Tree Level Order Traversal
Binary Tree Right Side View
Binary Tree Zigzag Level Order Traversal
Populating Next Right Pointers in Each Node II
Maximum Width of Binary Tree
Binary Tree Vertical Order Traversal
Populating Next Right Pointers in Each Node
Check Completeness of a Binary Tree
Binary Tree Preorder Traversal
Same Tree
Symmetric Tree
Binary Tree Paths
Convert Sorted Array to Binary Search Tree
Count Complete Tree Nodes
Sum of Left Leaves
Subtree of Another Tree
Path Sum II
Path Sum III
Longest Univalue Path
Maximum Difference Between Node and Ancestor
Construct Binary Tree from Preorder and Inorder Traversal
Construct Binary Tree from Inorder and Postorder Traversal
Serialize and Deserialize Binary Tree
Binary Tree Inorder Traversal
Minimum Distance Between BST Nodes
Minimum Absolute Difference in BST
Validate Binary Search Tree
Kth Smallest Element in a BST
Binary Search Tree Iterator
Balance a Binary Search Tree
Binary Tree Postorder Traversal
Invert Binary Tree
Diameter of Binary Tree
Balanced Binary Tree
Delete Nodes And Return Forest
Lowest Common Ancestor of a Binary Tree
Find Duplicate Subtrees
Flatten Binary Tree to Linked List
Distribute Coins in Binary Tree
Count Good Nodes in Binary Tree
Sum Root to Leaf Numbers
Boundary of Binary Tree
Step-By-Step Directions From a Binary Tree Node to Another
Binary Tree Maximum Path Sum

BST / Ordered Set

Introduction to BST
AVL Tree
Red Black Tree
Search in a Binary Search Tree
Closest Binary Search Tree Value
Two Sum IV - Input is a BST
Range Sum of BST
Trim a Binary Search Tree
Insert into a Binary Search Tree
Delete Node in a BST
Recover Binary Search Tree
Inorder Successor in BST
Inorder Successor in BST II
Lowest Common Ancestor of a Binary Search Tree
Construct Binary Search Tree from Preorder Traversal
Convert Binary Search Tree to Sorted Doubly Linked List
Largest BST Subtree
My Calendar I
My Calendar II
Stock Price Fluctuation

Heaps

Introduction to Heaps
Last Stone Weight
Furthest Building You Can Reach
Single-Threaded CPU
Process Tasks Using Servers
Minimum Cost to Connect Sticks
Longest Happy String
Maximum Performance of a Team
Find Median from Data Stream
IPO
Sliding Window Median
Find K Pairs with Smallest Sums
Kth Smallest Element in a Sorted Matrix
Merge k Sorted Lists
Smallest Range Covering Elements from K Lists
Introduction to Top K
Kth Largest Element in a Stream
Top K Frequent Elements
K Closest Points to Origin

Intervals

Introduction to Intervals
Summary Ranges
Meeting Rooms
Merge Intervals
Insert Interval
Remove Covered Intervals
Non-overlapping Intervals
Minimum Number of Arrows to Burst Balloons
Maximum Number of Events That Can Be Attended
Partition Labels
Meeting Rooms II
Meeting Scheduler
Car Pooling
Interval List Intersections
Two Best Non-Overlapping Events
Meeting Rooms III
Employee Free Time

Tries

Introduction to Trie
Implement Trie (Prefix Tree)
Design Add and Search Words Data Structure
Search Suggestions System
Longest Word in Dictionary
Replace Words
Remove Sub-Folders from the Filesystem
Find the Length of the Longest Common Prefix
Words Within Two Edits of Dictionary
Maximum XOR of Two Numbers in an Array
Word Search II
Stream of Characters
Concatenated Words
Word Squares
Palindrome Pairs

Data Structure Design

Implement Queue using Stacks
Implement Stack using Queues
Design Circular Queue
Design Circular Deque
Logger Rate Limiter
Design Hit Counter
Time Based Key-Value Store
Snapshot Array
Encode and Decode Strings
Insert Delete GetRandom O(1)
Design Browser History
LRU Cache
LFU Cache
Design Twitter
Design a Food Rating System
Maximum Frequency Stack
Max Stack
All O`one Data Structure
Range Module
Design Search Autocomplete System
Design In-Memory File System
Design a Text Editor

Greedy

Introduction to Greedy Algorithm
Assign Cookies
Apple Redistribution into Boxes
Jump Game II
Jump Game
Jump Game VII
Minimum Add to Make Parentheses Valid
Maximum Score From Removing Substrings
Gas Station
Task Scheduler
Queue Reconstruction by Height
Avoid Flood in The City
Most Profit Assigning Work
Maximum Swap
Maximum Matrix Sum
Candy
Minimum Number of Refueling Stops
Minimum Cost to Hire K Workers
Set Intersection Size At Least Two

Graphs

Introduction to Graphs
Depth-First Search
Breadth-First Search
Matrix Traversal
Multi-Source BFS
Cycle Detection in Undirected Graphs
Cycle Detection in Directed Graphs
Bipartite Graph Detection
A* Search Algorithm
Kosaraju's Algorithm
Tarjan's Algorithm
Flood Fill
Number of Islands
Number of Distinct Islands
Time Needed to Inform All Employees
All Paths From Source to Target
Clone Graph
Is Graph Bipartite?
All Nodes Distance K in Binary Tree
Employee Importance
Surrounded Regions
Pacific Atlantic Water Flow
Word Search
Number of Enclaves
Making A Large Island
Critical Connections in a Network
Longest Path With Different Adjacent Characters
Rotting Oranges
01 Matrix
Open the Lock
Snakes and Ladders
Minimum Genetic Mutation
Walls and Gates
Minimum Knight Moves
Shortest Path in Binary Matrix
Path With Maximum Minimum Value
Word Ladder
Bus Routes
Minimum Obstacle Removal to Reach Corner
Shortest Path in a Grid with Obstacles Elimination
Introduction to Topological Sort
Course Schedule II
Find Eventual Safe States
Minimum Height Trees
Course Schedule IV
Parallel Courses
Find All Possible Recipes from Given Supplies
Alien Dictionary
Sort Items by Groups Respecting Dependencies
Introduction to Union Find
Number of Provinces
Redundant Connection
Accounts Merge
Number of Connected Components in an Undirected Graph
Graph Valid Tree
Evaluate Division
Most Stones Removed with Same Row or Column
Number of Islands II
Minimize Malware Spread
Min Cost to Connect All Points
Connecting Cities With Minimum Cost
Optimize Water Distribution in a Village
Find Critical and Pseudo-Critical Edges in Minimum Spanning Tree
Maximize Spanning Tree Stability with Upgrades
Introduction to Shortest Path
Dijkstra's Algorithm
Bellman-Ford Algorithm
Floyd-Warshall Algorithm
Network Delay Time
Cheapest Flights Within K Stops
Path with Maximum Probability
Path With Minimum Effort
The Maze II
Minimum Cost to Convert String I
Minimum Cost Path with Edge Reversals
Find Minimum Time to Reach Last Room I
Swim in Rising Water
Minimum Cost to Make at Least One Valid Path in a Grid
Minimum Weighted Subgraph With the Required Paths
Reconstruct Itinerary
Cracking the Safe
Valid Arrangement of Pairs

Dynamic Programming

Advanced Topics

Introduction to Pattern Matching
Brute Force Pattern Matching
KMP Algorithm
Rabin-Karp Algorithm
Z-Algorithm
Suffix Arrays
Repeated Substring Pattern
Repeated String Match
Number of Distinct Substrings in a String
Shortest Palindrome
Longest Happy Prefix
Longest Duplicate Substring
Fenwick Tree (Binary Indexed Tree)
Segment Tree
Segment Tree with Lazy Propagation
Range Sum Query - Mutable
Range Sum Query 2D - Mutable
Count of Smaller Numbers After Self
Falling Squares
Block Placement Queries
Longest Balanced Subarray II
Number of Pairs Satisfying Inequality
Minimum Interval to Include Each Query
The Skyline Problem
Rectangle Area II
Perfect Rectangle

Frequency of the Most Frequent Element

Frequency

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