leetcode 48. 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.

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]
]

思路：

先把矩陣轉(zhuǎn)置，然后將每一行反轉(zhuǎn)

var rotate = function(matrix) {
    for(var i=0;i<matrix.length;i++){
        for(j=i+1;j<matrix.length;j++){
            var temp=matrix[i][j];
            matrix[i][j]=matrix[j][i];
            matrix[j][i]=temp;
        }
        matrix[i].reverse();
       
    }
};