Leetcode Rotate Image

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?

思路：坐标是i,j的元素旋转90坐标变成了j,n-i+1

首先将矩阵倒置，那么i,j元素会变成n-i+1,j. 如果想变成j,n-i+1。 则直接交换就ok

AC 代码

class Solution:
    # @param matrix, a list of lists of integers
    # @return a list of lists of integers
    def rotate(self, matrix):
        matrix.reverse()
        length = len(matrix)
        for i in range(0,length):
            for j in range(i+1, length):
                matrix[i][j], matrix[j][i] = matrix[j][i], matrix[i][j]
        return matrix