A comprehensive collection of coding challenges from multiple platforms for learning data structures, algorithms, and frontend engineering.
| Platform | Focus Area | Problems Solved |
|---|---|---|
| LeetCode | Data Structures & Algorithms | 169 |
| GreatFrontEnd | Frontend Engineering | 9 |
Various places where I enjoy practicing solving coding challenges:
Focus: Data structures, algorithms, and problem-solving patterns
Progress:
- Easy: 80 problems
- Medium: 75 problems
- Hard: 14 problems
Quick Links:
Resources:
Focus: Frontend engineering, JavaScript fundamentals, and system design
Progress:
- GFE 75: 5/75 problems
- Blind 75: 4/75 problems
Quick Links:
- Browse GreatFrontEnd Solutions →
- GreatFrontEnd Platform Guide →
- GFE 75 Progress →
- Blind 75 Progress →
Coming Soon:
- Frontend System Design
- Hash Lookup - O(1) lookups with hash tables
- Two Pointers - Efficient array traversal
- Sliding Window - Subarray/substring problems
- AI/LLM-Oriented Problems - Algorithms that map to generative AI fundamentals
- Gradient Descent - Optimization technique for machine learning
- Math Problems - Number theory and mathematical algorithms
- More topic guides coming soon...
- Interview Workflow - Conduct AI-assisted technical interviews
- Code Review Guidelines - Standards for this repository
Easy Problems (80 solved)
- 0001 - Two Sum
- 0009 - Palindrome Number
- 0020 - Valid Parentheses
- 0121 - Best Time to Buy and Sell Stock
- 0169 - Majority Element
- 0266 - Palindrome Permutation
- 0303 - Range Sum Query - Immutable
- 0205 - Isomorphic Strings
- 2168 - Check if Numbers Are Ascending in a Sentence
- 0383 - Ransom Note
- 0485 - Max Consecutive Ones
- 0551 - Student Attendance Record I
- 0598 - Range Addition II
- 0628 - Maximum Product of Three Numbers
- 0643 - Maximum Average Subarray I
- 0645 - Set Mismatch
- 0724 - Find Pivot Index
- 0777 - Toeplitz Matrix
- 0837 - Most Common Word
- 0841 - Shortest Distance to a Character
- 0898 - Transpose Matrix
- 0924 - Fair Candy Swap
- 0941 - Sort Array by Parity
- 0958 - Sort Array By Parity II
- 1044 - Find Common Characters
- 1083 - Two Sum Less Than K
- 1098 - Largest Unique Number
- 1319 - Unique Number of Occurrences
- 1363 - Greatest English Letter in Upper and Lower Case
- 1476 - Count Negative Numbers in a Sorted Matrix
- 1482 - How Many Numbers Are Smaller Than the Current Number
- 1580 - Shuffle the Array
- 1741 - Sort Array by Increasing Frequency
- 2102 - Find the Middle Index in Array
- 2331 - Intersection of Multiple Arrays
- 2614 - Maximum Count of Positive Integer and Negative Integer
- 2624 - Difference Between Element Sum and Digit Sum of an Array
- 2634 - Minimum Common Value
- 2639 - Separate the Digits in an Array
- 2654 - Count the Number of Vowel Strings in Range
- 2737 - Row With Maximum Ones
- 3034 - Points That Intersect With Cars
- 3207 - Make Three Strings Equal
- 3429 - Special Array I
- 3581 - The Two Sneaky Numbers of Digitville
- 3859 - Maximum Product of Two Digits
- 2902 - Max Pair Sum in an Array
- 1127 - Last Stone Weight
- 2316 - Count Hills and Valleys in an Array
- 1241 - Decompress Run-Length Encoded List
- 1302 - Delete Characters to Make Fancy String
- 2032 - Largest Odd Number in String
- 2058 - Concatenation of Array
- 2542 - Average Value of Even Numbers That Are Divisible by Three
- 2767 - Maximum Sum With Exactly K Elements
- 2361 - Calculate Digit Sum of a String
- 2756 - Buy Two Chocolates
- 3172 - Divisible and Non-divisible Sums Difference
- 1039 - Find the Town Judge
- 1916 - Find Center of Star Graph
- 2121 - Find if Path Exists in Graph
- 0070 - Climbing Stairs
- 0171 - Excel Sheet Column Number
- 0268 - Missing Number
- 0476 - Number Complement
- 1289 - Day of the Week
- 1920 - Determine Color of a Chessboard Square
- 3055 - Maximum Odd Binary Number
- 3371 - Harshad Number
Medium Problems (75 solved)
- 0003 - Longest Substring Without Repeating Characters
- 0016 - 3Sum Closest
- 0018 - 4Sum
- 0031 - Next Permutation
- 0034 - Find First and Last Position of Element in Sorted Array
- 0073 - Set Matrix Zeroes
- 0080 - Remove Duplicates from Sorted Array II
- 0090 - Subsets II
- 0209 - Minimum Size Subarray Sum
- 0287 - Find the Duplicate Number
- 0324 - Wiggle Sort II
- 0487 - Max Consecutive Ones II
- 0658 - Find K Closest Elements
- 2868 - Continuous Subarrays
- 3241 - Divide Array Into Arrays With Max Difference
- 0002 - Add Two Numbers
- 0019 - Remove Nth Node From End of List
- 0061 - Rotate List
- 0082 - Remove Duplicates from Sorted List II
- 0086 - Partition List
- 0142 - Linked List Cycle II
- 0148 - Sort List
- 0159 - Longest Substring with At Most Two Distinct Characters
- 0165 - Compare Version Numbers
- 0187 - Repeated DNA Sequences
- 0340 - Longest Substring with At Most K Distinct Characters
- 0395 - Longest Substring with At Least K Repeating Characters
- 0438 - Find All Anagrams in a String
- 0616 - Add Bold Tag in String
- 0692 - Top K Frequent Words
- 0760 - Bold Words in String
- 2487 - Optimal Partition of String
- 0053 - Maximum Subarray
- 0072 - Edit Distance
- 0139 - Word Break
- 0198 - House Robber
- 0413 - Arithmetic Slices
- 0718 - Maximum Length of Repeated Subarray
- 1250 - Longest Common Subsequence
- 0012 - Integer to Roman
- 1359 - Circular Permutation in Binary Representation
- 1585 - The kth Factor of n
- 1674 - Minimum Operations to Make Array Equal
- 0133 - Clone Graph
- 0207 - Course Schedule
- 0210 - Course Schedule II
- 0261 - Graph Valid Tree
- 0277 - Find the Celebrity
- 0310 - Minimum Height Trees
- 0323 - Number of Connected Components in an Undirected Graph
- 0511 - All Paths from Source Lead to Destination
- 0444 - Sequence Reconstruction
- 0505 - The Maze II
- 0684 - Redundant Connection
- 0744 - Network Delay Time
- 0803 - Cheapest Flights Within K Stops
- 0813 - All Paths From Source to Target
- 0820 - Find Eventual Safe States
- 0871 - Keys and Rooms
- 0881 - Loud and Rich
- 0922 - Possible Bipartition
- 0984 - Most Stones Removed with Same Row or Column
- 1100 - Connecting Cities With Minimum Cost
- 1101 - Parallel Courses
- 1120 - Flower Planting With No Adjacent
- 1229 - Shortest Path with Alternating Colors
- 1442 - Number of Operations to Make Network Connected
- 2035 - Count Sub Islands
- 2090 - Number of Ways to Arrive at Destination
- 3677 - Maximum Amount of Money Robot Can Earn
Hard Problems (14 solved)
- 0115 - Distinct Subsequences
- 0689 - Maximum Sum of 3 Non-Overlapping Subarrays
- 1034 - Subarrays with K Different Integers
- 0269 - Alien Dictionary
- 0329 - Longest Increasing Path in a Matrix
- 0332 - Reconstruct Itinerary
- 0499 - The Maze III
- 0685 - Redundant Connection II
- 0754 - Cracking the Safe
- 0770 - Couples Holding Hands
- 0863 - Sum of Distances in Tree
- 0877 - Shortest Path Visiting All Nodes
- 2439 - Longest Cycle in a Graph
- 0016 - 3Sum Closest - Medium
- 0018 - 4Sum - Medium
- 0080 - Remove Duplicates from Sorted Array II - Medium
- More in docs →
- 0003 - Longest Substring Without Repeating Characters - Medium
- 0159 - Longest Substring with At Most Two Distinct Characters - Medium
- 0209 - Minimum Size Subarray Sum - Medium
- 0340 - Longest Substring with At Most K Distinct Characters - Medium
- More in docs →
- 0001 - Two Sum - Easy
- 0383 - Ransom Note - Easy
- More in docs →
- 0053 - Maximum Subarray - Medium
- 0070 - Climbing Stairs - Easy
- 0198 - House Robber - Medium
- 0133 - Clone Graph - Medium
- 0207 - Course Schedule - Medium
- 0210 - Course Schedule II - Medium
Each problem directory contains:
README.md- Problem description and examples- Solution file(s) in JavaScript/TypeScript
- Test files (where applicable) using Vitest
- Auto-generated analysis files in
docs/analysis/
# Navigate to a problem directory
cd leetcode/easy/0001-two-sum
# Run the solution
node two-sum.js
# Or with TypeScript
npx ts-node two-sum.ts# Install dependencies
npm install
# Run all tests in watch mode
npm test
# Run tests once (CI mode)
npm run test:run
# Run tests with interactive UI
npm run test:ui
# Generate coverage report
npm run test:coverage
# Run specific test
npm test -- two-sum.test# Quick quality check (lint + format check)
npm run quality:check
# Fix linting and formatting issues
npm run quality:fix
# Comprehensive quality analysis
npm run quality:full
# Analyze algorithm complexity
npm run complexity:leetcodeThis repository uses Vitest for fast, modern testing:
- Watch Mode: Automatically re-runs tests on file changes
- UI Mode: Visual interface for viewing and debugging tests
- Coverage: Built-in code coverage with v8
- TypeScript: First-class TypeScript support
See Testing Guide for detailed instructions.
Automated quality system includes:
- ESLint: Code style and quality enforcement
- Prettier: Consistent code formatting
- Complexity Analyzer: Automated Big O analysis
- Pre-commit Hooks: Quality gates (optional)
- CI/CD Workflows: Automated checks on PRs
See Code Quality Guide for details.
Multiple specialized AI agents maintain code quality and create educational documentation:
- DSA Code Reviewer: Reviews algorithm solutions and provides complexity analysis
- Test Case Generator: Creates comprehensive test cases
- Algorithmic Pattern Spotter: Identifies and documents patterns
See AGENTS.md for comprehensive agent guidelines.
This is a personal learning repository, but suggestions and improvements are welcome! Please follow the guidelines in CLAUDE.md when contributing.
All solutions in this repository follow strict review guidelines. See CLAUDE.md for:
- Algorithm correctness criteria
- Complexity analysis standards
- Code quality expectations
- DSA learning focus areas
- Platform-specific guidelines (LeetCode, GreatFrontEnd)
This repository includes an automated spaced repetition system for problem review:
- Reviews scheduled at 1, 3, 7, 14, and 30 days after solving
- Automatic GitHub issue creation for review reminders
- Progress tracking in
docs/reviews/review-schedule.json
Learn more: Interview Workflow Documentation