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59 lines
1.5 KiB
Plaintext
59 lines
1.5 KiB
Plaintext
---
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title: '48. Rotate Image'
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description: You are given an n x n 2D matrix representing an image, rotate the image by 90 degrees (clockwise)
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icon: line-dot-left-horizontal
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sidebar:
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label: 'Rotate Image'
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badge: 'Medium'
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---
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<Badge variant="accent">Array</Badge>
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### Example 1:
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- Input: `matrix = [[1,2,3],[4,5,6],[7,8,9]]`
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- Output: `[[7,4,1],[8,5,2],[9,6,3]]`
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### Example 2:
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- Input: `matrix = [[5,1,9,11],[2,4,8,10],[13,3,6,7],[15,14,12,16]]`
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- Output: `[[15,13,2,5],[14,3,4,1],[12,6,8,9],[16,7,10,11]]`
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### Constraints:
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- `n == matrix.length == matrix[i].length`
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- `1 <= n <= 20`
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- `-1000 <= matrix[i][j] <= 1000`
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## Approach
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```mermaid
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flowchart TD
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S(["rotate(matrix)"]) --> N["n = len(matrix)"]
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N --> F{"more r in range(n)?"}
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F -- yes --> G{"more c in range(r + 1, n)?"}
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G -- yes --> T["swap matrix[r][c] and matrix[c][r] — transpose across the diagonal"]
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T --> G
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G -- no --> F
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F -- no --> H{"more r in range(n)?"}
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H -- yes --> R["matrix[r].reverse() — transpose then mirror is a clockwise turn"]
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R --> H
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H -- no --> E(["return None — rotated in place"])
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```
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## Solution
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```py
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class Solution:
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def rotate(self, matrix: List[List[int]]) -> None:
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n = len(matrix)
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for r in range(n):
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for c in range(r + 1, n):
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matrix[r][c], matrix[c][r] = matrix[c][r], matrix[r][c]
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for r in range(n):
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matrix[r].reverse()
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```
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## Explanation
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<YouTube id="fMSJSS7eO1w" title="Rotate Image - Matrix - Leetcode 48" />
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