Prefix Sum
Total Problems: 9
Completed: 9 (100%)
📚 Pattern Master Notes
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 | 2 | 2 | 0 | 100% |
| 🟡 Medium | 6 | 6 | 0 | 100% |
| 🔴 Hard | 1 | 1 | 0 | 100% |
Problems
| # | Problem | Difficulty | Status | Confidence |
|---|---|---|---|---|
| 46 | Range Sum Query - Immutable | E | ✅ | HGH |
| 47 | Find Pivot Index | E | ✅ | HGH |
| 48 | Product of Array Except Self | M | ✅ | HGH |
| 49 | Range Sum Query 2D - Immutable | M | ✅ | LOW |
| 50 | Continuous Subarray Sum | M | ✅ | MED |
| 51 | Contiguous Array | M | ✅ | MED |
| 52 | Subarray Sum Equals K | M | ✅ | HGH |
| 53 | Subarray Sums Divisible by K | M | ✅ | HGH |
| 54 | Maximum Subarray | H | ✅ | LOW |
Last Updated: 2026-02-13 19:40:00
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