Leetcode||48. Rotate Image

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最新推荐文章于 2025-07-24 15:44:24 发布

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本文介绍了一种高效的二维数组顺时针旋转90度的算法，通过先进行矩阵转置再对每行进行翻转的方式实现。该方法无需额外空间，在原地修改输入矩阵。

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You are given an n x n 2D matrix representing an image.

Rotate the image by 90 degrees (clockwise).

Note:
You have to rotate the image in-place, which means you have to modify the input 2D matrix directly. DO NOT allocate another 2D matrix and do the rotation.

Example 1:

Given input matrix = 
[
  [1,2,3],
  [4,5,6],
  [7,8,9]
],

rotate the input matrix in-place such that it becomes:
[
  [7,4,1],
  [8,5,2],
  [9,6,3]
]

Example 2:

Given input matrix =
[
  [ 5, 1, 9,11],
  [ 2, 4, 8,10],
  [13, 3, 6, 7],
  [15,14,12,16]
], 

rotate the input matrix in-place such that it becomes:
[
  [15,13, 2, 5],
  [14, 3, 4, 1],
  [12, 6, 8, 9],
  [16, 7,10,11]
]

二维数组顺时针旋转90°可以等同于将一个二维数组转置（行列互换），然后每行翻转。

class Solution(object):
    def rotate(self, matrix):
        """
        :type matrix: List[List[int]]
        :rtype: void Do not return anything, modify matrix in-place instead.
        """
        size = len(matrix)
        for i in range(size):
            for j in range(i + 1,size):
                matrix[i][j],matrix[j][i] = matrix[j][i],matrix[i][j]
        for i in range(size):
            matrix[i].reverse()