48. 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?

标准方法，先把矩阵上下颠倒，然后再根据左上至右下的对角线对称反转：
1 2 3 => 7 8 9 => 7 4 1
4 5 6 => 4 5 6 => 8 5 2
7 8 9 => 1 2 3 => 9 6 3

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

我想到了一个新的，哈哈哈，谁能看懂～

var rotate = function(matrix) {
    var n = matrix.length;
    var buff_len = n-1;
    var count = 0;
    while (buff_len>0) {
        var a = count;
        var b = count+buff_len;
        for (var i = 0;i < buff_len;i++) {
            var temp1 = matrix[a+i][b];
            matrix[a+i][b] = matrix[a][a+i];
            var temp2 = matrix[b][b-i];
            matrix[b][b-i] = temp1;
            var temp3 = matrix[b-i][a];
            matrix[b-i][a] = temp2;
            matrix[a][a+i] = temp3;
        }
        count++;
        buff_len-=2;
    } 
};

就是从最外圈开始，一圈一圈的换。