Rotate Image
Rotate an n × n matrix by 90 degrees clockwise, in place.
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Lesson notes
Try it before you watch
Restate the problem in your own words, list the edge cases, and sketch a solution with its running time. Then play the video and compare.
Reveal the key idea
Transpose the matrix (swap across the main diagonal), then reverse every row.
Pattern: Matrices & grids. Keep row and column boundaries explicit and treat grid cells as graph nodes when needed.
Complexity
| Measure | Bound |
|---|---|
| Time | O(n²) |
| Extra space | O(1) |
Walkthroughs often start from a simpler approach first; aim to reach these bounds. New to Big-O? Read understanding algorithmic complexity.