Lean
4
Language
Tactics
Playground
Academy
Problems
Pricing
Search
⌘K
Problems
All problems
Problems
Leaderboard
Ranking
My progress
Progress
Courses →
Get the
Pass · €10
Problems
/
25
25. N-Queens
Hard
Program
Academy Pass
Opening the problem…
Similar problems
7. Valid parentheses
Medium
16. Run-length encoding
Medium
6. Climbing stairs
Easy
13. Digit sum
Easy
← 24. Best time to buy and sell
26. Merge two sorted lists →