🎯 LeetCode Difficulty Estimator
Paste any coding problem and instantly predict whether it's Easy, Medium, or Hard. Analyzes constraints, algorithm signals, data structures, and complexity patterns.
📊 Difficulty Breakdown
🔢 Constraint → Difficulty
| n (input size) | Expected complexity | Hint |
|---|---|---|
| ≤ 20 | O(2ⁿ) / O(n!) | Easy–Hard, brute-force OK |
| ≤ 500 | O(n²) | Easy–Medium |
| ≤ 10,000 | O(n²) | Medium |
| ≤ 100,000 | O(n log n) | Medium–Hard |
| ≤ 10^6 | O(n) | Hard (linear only) |
| ≤ 10^9 | O(log n) | Hard (math/binary) |
💬 What to include
- ✅ Full problem statement
- ✅ Constraints section (n ≤ …)
- ✅ Example input/output (optional)
- ⚠️ The more text, the better the signal
Frequently Asked Questions
How does LeetCode decide if a problem is Easy, Medium, or Hard? +
Difficulty is set by the problem author and refined by community acceptance rates and ratings. Key signals include constraint sizes, required algorithms (DP, graph traversal, advanced data structures), and how many non-obvious insights are needed to reach the optimal solution.
What makes a LeetCode problem Hard? +
Hard problems typically require: advanced data structures (segment trees, tries, BITs), complex DP with 2D/3D state spaces, graph algorithms with extra constraints, mathematical number theory, or combining 2+ non-obvious techniques. Very large constraints (n up to 10⁹) that require O(log n) or O(1) solutions also indicate Hard.
How can I estimate difficulty just by reading a problem? +
Key signals: constraint size (10⁵–10⁶ → Medium/Hard, ≤ 10⁴ → Easy/Medium), phrases like "minimum cost", "number of ways", "maximum profit" with large n → DP (Medium/Hard), presence of graphs/trees with extra rules → Hard, straightforward array/string manipulation → Easy.