int t; cin >> t; while (t--) // solve here

| Input size (n) | Required complexity | |----------------|----------------------| | ≤ 20 | O(2ⁿ) (backtracking) | | ≤ 100 | O(n³) | | ≤ 2000 | O(n²) | | ≤ 100,000 | O(n log n) | | ≥ 1,000,000 | O(n), O(log n) |

Competitive programming (CP) is more than just coding—it’s a mental sport. You’re given a problem, usually with strict time and memory limits, and you must write a program that solves it correctly and efficiently. Over the years, a core set of essentials has emerged, separating raw coding ability from true contest readiness.