Arrays & Hashing
Total Problems: 20
Completed: 20 (100%)
📚 Pattern Master Notes
Arrays & Hashing - Complete Guide
This comprehensive guide includes: - 🧠 Pattern recognition & problem-solving mindset - 🎯 Sub-patterns and variations - 🏆 Golden templates and code examples - ⚠️ Common pitfalls and debugging tips - 📊 Decision trees and quick reference tables
💡 Tip: Read the notes before starting problems to build intuition!
Progress by Difficulty
| Difficulty | Total | Completed | Remaining | Percentage |
|---|---|---|---|---|
| 🟢 Easy | 8 | 8 | 0 | 100% |
| 🟡 Medium | 10 | 10 | 0 | 100% |
| 🔴 Hard | 2 | 2 | 0 | 100% |
Problems
| # | Problem | Difficulty | Status | Confidence |
|---|---|---|---|---|
| 1 | Two Sum | E | ✅ | HGH |
| 2 | Longest Common Prefix | E | ✅ | HGH |
| 3 | Length of Last Word | E | ✅ | HGH |
| 4 | Best Time to Buy and Sell Stock | E | ✅ | HGH |
| 5 | Contains Duplicate | E | ✅ | HGH |
| 6 | Valid Anagram | E | ✅ | HGH |
| 7 | Is Subsequence | E | ✅ | HGH |
| 8 | Replace Elements with Greatest Element on Right Side | E | ✅ | HGH |
| 9 | Valid Sudoku | M | ✅ | HGH |
| 10 | Group Anagrams | M | ✅ | HGH |
| 11 | Sort Colors | M | ✅ | MED |
| 12 | Longest Consecutive Sequence | M | ✅ | MED |
| 13 | Product of Array Except Self | M | ✅ | HGH |
| 14 | Encode and Decode Strings | M | ✅ | HGH |
| 15 | Top K Frequent Elements | M | ✅ | MED |
| 16 | Find All Anagrams in a String | M | ✅ | MED |
| 17 | Subarray Sum Equals K | M | ✅ | MED |
| 18 | String Encode and Decode | M | ✅ | HGH |
| 19 | Longest Substring Without Repeating Characters | H | ✅ | MED |
| 20 | First Missing Positive | H | ✅ | MED |
Last Updated: 2026-02-13 19:40:00
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