Array

048. Rotate Image

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.

即
对给定矩阵进行旋转，但是不能用额外的空间

Solutions

很简单的想法：
先转置，和互换
然后对每一行元素取反

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