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Free Pattern Library

Start with 4 core categories and 45 problems. No account needed. Upgrade to Pro when you want all 14 categories and 250 problems.

Arrays & Hashing

Free15 problems
  • Two Sum
  • Contains Duplicate
  • Valid Anagram
  • Group Anagrams
  • Top K Frequent Elements

Two Pointers

Free12 problems
  • Valid Palindrome
  • Two Sum II
  • 3Sum
  • Container With Most Water

Sliding Window

Free10 problems
  • Best Time to Buy & Sell Stock
  • Longest Substring Without Repeating
  • Longest Repeating Character Replacement

Stack

Free8 problems
  • Valid Parentheses
  • Min Stack
  • Evaluate Reverse Polish Notation
  • Daily Temperatures

Binary Search

Pro18 problems
  • Search in Rotated Sorted Array
  • Find Minimum in Rotated Array
  • Koko Eating Bananas

Trees

Pro22 problems
  • Invert Binary Tree
  • Maximum Depth
  • Same Tree

Dynamic Programming

Pro24 problems
  • Climbing Stairs
  • House Robber
  • Coin Change

Graphs

Pro20 problems
  • Number of Islands
  • Clone Graph
  • Course Schedule

Unlock all 250 problems

All 14 patterns, company-specific mappings, and solution walkthroughs included.

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