Rotate Image
Rotate Image is a medium Math & Geometry problem from the Blind 75. The key pattern is transpose + reverse, and a good solution runs in O(n²) time.
Problem
Rotate a square matrix 90 degrees clockwise and print the resulting matrix.
Examples
Example 1
Input
[[1,2,3],[4,5,6],[7,8,9]]Output
[[7,4,1],[8,5,2],[9,6,3]]Example 2
Input
[[1,2],[3,4]]Output
[[3,1],[4,2]]Example 3
Input
[[4,8,1,6],[2,7,3,9],[5,0,11,12],[13,14,15,10]]Output
[[13,5,2,4],[14,0,7,8],[15,11,3,1],[10,12,9,6]]Approach
Transpose the matrix across its main diagonal, then reverse each row to rotate it 90° clockwise in place.
| Pattern | Transpose + reverse |
|---|---|
| Time | O(n²) |
| Space | O(1) |
Watch out for
Reversing columns instead of rows rotates the other way.