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leetcode解题-rotate image

admin 11月 11, 2020 0

描述

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

Rotate the image by 90 degrees (clockwise).

Follow up:
Could you do this in-place?

分析

将矩阵顺时针旋转90°，等同于先沿水平中线翻转，再按主对角线翻转。

代码

Python

class (object):
    def rotate(self, matrix):
        """
        :type matrix: List[List[int]]
        :rtype: void Do not return anything, modify matrix in-place instead.
        """
        n = len(matrix)
        for i in xrange(n / 2):
            for j in xrange(n):
                matrix[i][j], matrix[n - 1 - i][j] = matrix[n - 1 - i][j], matrix[i][j]

        for i in xrange(n):
            for j in xrange(i):
                matrix[i][j], matrix[j][i] = matrix[j][i], matrix[i][j]