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300 problems organized by pattern and difficulty. Free tier includes 135 problems. Upgrade to Pro for all 300.
| Status | Title | Difficulty |
|---|---|---|
| Backspace String Compare | Easy | |
| Balanced Binary Tree | Easy | |
| Best Time to Buy and Sell Stock | Easy | |
| Best Time to Buy and Sell Stock | Easy |
Upgrade to access the full problem library with solutions, test cases, and in-browser code execution.
Upgrade to Pro| Binary Search | Easy |
| Climbing Stairs | Easy |
| Combine Two Tables | Easy |
| Concatenation of Array | Easy |
| Contains Duplicate | Easy |
| Contains Duplicate II | Easy |
| Counting Bits | Easy |
| Diameter of Binary Tree | Easy |
| First Unique Character in a String | Easy |
| Happy Number | Easy |
| Happy Number Math | Easy |
| Implement strStr() | Easy |
| Invert Binary Tree | Easy |
| Isomorphic Strings | Easy |
| Is Subsequence | Easy |
| Linked List Cycle | Easy |
| Longest Common Prefix | Easy |
| Lucky Numbers in a Matrix | Easy |
| Majority Element | Easy |
| Maximum Depth of Binary Tree | Easy |
| Meeting Rooms | Easy |
| Merge Sorted Array | Easy |
| Merge Two Sorted Lists | Easy |
| Missing Number | Easy |
| Move Zeroes | Easy |
| Next Greater Element I | Easy |
| Number of 1 Bits | Easy |
| Palindrome Linked List | Easy |
| Palindrome Number | Easy |
| Path Sum | Easy |
| Plus One | Easy |
| Ransom Note | Easy |
| Remove Duplicates from Sorted Array | Easy |
| Remove Duplicates from Sorted List | Easy |
| Remove Element | Easy |
| Reverse Bits | Easy |
| Reverse Linked List | Easy |
| Roman to Integer | Easy |
| Same Tree | Easy |
| Search Insert Position | Easy |
| Single Number | Easy |
| Sqrt(x) | Easy |
| Sqrt(x) Math | Easy |
| Squares of a Sorted Array | Easy |
| Subtree of Another Tree | Easy |
| Toeplitz Matrix | Easy |
| Two Sum | Easy |
| Valid Anagram | Easy |
| Valid Palindrome | Easy |
| Valid Palindrome II | Easy |
| Valid Parentheses | Easy |
| Word Pattern | Easy |
| 3Sum | Medium |
| Agent Memory Manager | Medium |
| Best Time to Buy and Sell Stock II | Medium |
| Best Time to Buy and Sell Stock III | Medium |
| Binary Search in Rotated Sorted Array | Medium |
| Binary Search Tree Operations | Medium |
| Binary Search Tree Operations | Medium |
| Binary Tree Maximum Path Sum | Medium |
| COBOL Numeric Storage Decoder | Medium |
| Container With Most Water | Medium |
| DB2 Cursor Statement Validator | Medium |
| Debounce Function | Medium |
| Dining Philosophers: Deadlock-Free Resource Allocation | Medium |
| Distributed Rate Limiter | Medium |
| Distributed Rate Limiter | Medium |
| Duplicate Insert Error Handler | Medium |
| Employees Earning More Than Their Manager | Medium |
| Employees Earning More Than Their Manager | Medium |
| Find Median from Data Stream | Medium |
| Find Minimum in Rotated Sorted Array | Medium |
| Find the Duplicate Number | Medium |
| Group Anagrams | Medium |
| High-Frequency Claimants | Medium |
| Implement Debounce | Medium |
| Island Perimeter | Medium |
| JCL Job Step Sequencer for COBOL File Processing | Medium |
| Job Log Analyzer | Medium |
| K Closest Hotels | Medium |
| K Closest Hotels | Medium |
| Kth Smallest Element in a BST | Medium |
| Longest Common Subsequence | Medium |
| Longest Substring Without Repeating Characters | Medium |
| Loop Simulation: UNTIL vs VARYING | Medium |
| LRU Cache | Medium |
| LRU Cache | Medium |
| Maximum Product Subarray | Medium |
| Maximum Subarray | Medium |
| Maximum Sum Subarray of Size K | Medium |
| Median of Two Sorted Arrays | Medium |
| Memoization Cache Simulator | Medium |
| Memoization Cache Simulator | Medium |
| Merge Two Sorted Linked Lists | Medium |
| Module Call Resolver | Medium |
| Net Revenue Per Account | Medium |
| Network Shortest Path | Medium |
| Next Permutation | Medium |
| Pair Sum Finder | Medium |
| Payment API Rate Limiter | Medium |
| Peak Concurrent Bookings | Medium |
| Peak Concurrent Bookings | Medium |
| Product Inventory REST API | Medium |
| Product of Array Except Self | Medium |
| Prompt Strategy Classifier | Medium |
| Rate Limiter for Hotel Search API | Medium |
| ReAct Agent Simulator | Medium |
| Real-Time Transaction Anomaly Detector | Medium |
| Request Scheduler: Minimum Threads for Concurrent Processing | Medium |
| Reverse Words in a String | Medium |
| Rotate Array | Medium |
| Rotate Matrix 90 Degrees Clockwise | Medium |
| Search in Rotated Sorted Array | Medium |
| Serialize and Deserialize Binary Tree | Medium |
| Shared Memory Parameter Passing | Medium |
| Shortest Path in Binary Matrix | Medium |
| Sort Colors | Medium |
| Stock Trader with K Transactions | Medium |
| Subarray Sum Equals K with Bounded Window | Medium |
| Suspicious Transaction Detector | Medium |
| Suspicious Transaction Detector | Medium |
| Task Scheduler Simulator | Medium |
| Task Scheduler with Dependencies | Medium |
| Thread-Safe Bounded Producer-Consumer Queue | Medium |
| Thread-Safe Singleton | Medium |
| Thread-Safe Singleton Logger | Medium |
| Top 3 Most Booked Hotel Categories | Medium |
| Top K Frequent Transactions | Medium |
| Transaction Deduplication | Medium |
| Two Sum II - Input Array Is Sorted | Medium |
| Visa Application Processing Order | Medium |