mirror of
https://github.com/prdlk/leetcode.git
synced 2026-11-02 13:12:44 +00:00
58 lines
1.4 KiB
Plaintext
58 lines
1.4 KiB
Plaintext
---
|
|
title: '48. Rotate Image'
|
|
description: You are given an n x n 2D matrix representing an image, rotate the image by 90 degrees (clockwise)
|
|
sidebar:
|
|
label: 'Rotate Image'
|
|
badge: 'Medium'
|
|
---
|
|
|
|
<Badge variant="accent">Array</Badge>
|
|
|
|
### Example 1:
|
|
- Input: `matrix = [[1,2,3],[4,5,6],[7,8,9]]`
|
|
- Output: `[[7,4,1],[8,5,2],[9,6,3]]`
|
|
|
|
### Example 2:
|
|
- Input: `matrix = [[5,1,9,11],[2,4,8,10],[13,3,6,7],[15,14,12,16]]`
|
|
- Output: `[[15,13,2,5],[14,3,4,1],[12,6,8,9],[16,7,10,11]]`
|
|
|
|
### Constraints:
|
|
|
|
- `n == matrix.length == matrix[i].length`
|
|
- `1 <= n <= 20`
|
|
- `-1000 <= matrix[i][j] <= 1000`
|
|
|
|
## Approach
|
|
|
|
```mermaid
|
|
flowchart TD
|
|
S(["rotate(matrix)"]) --> N["n = len(matrix)"]
|
|
N --> F{"more r in range(n)?"}
|
|
F -- yes --> G{"more c in range(r + 1, n)?"}
|
|
G -- yes --> T["swap matrix[r][c] and matrix[c][r] — transpose across the diagonal"]
|
|
T --> G
|
|
G -- no --> F
|
|
F -- no --> H{"more r in range(n)?"}
|
|
H -- yes --> R["matrix[r].reverse() — transpose then mirror is a clockwise turn"]
|
|
R --> H
|
|
H -- no --> E(["return None — rotated in place"])
|
|
```
|
|
|
|
## Solution
|
|
|
|
```py
|
|
class Solution:
|
|
def rotate(self, matrix: List[List[int]]) -> None:
|
|
n = len(matrix)
|
|
for r in range(n):
|
|
for c in range(r + 1, n):
|
|
matrix[r][c], matrix[c][r] = matrix[c][r], matrix[r][c]
|
|
|
|
for r in range(n):
|
|
matrix[r].reverse()
|
|
```
|
|
|
|
## Explanation
|
|
|
|
<YouTube id="fMSJSS7eO1w" title="Rotate Image - Matrix - Leetcode 48" />
|