leetcode48.旋转图像

将二维矩阵顺时针旋转90度

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感觉就是个数学问题。。最上面和最下面的行两两交换，然后在交换上三角和下三角的值即可

  public void rotate(int[][] matrix) {
        int m = matrix.length;
        if (m == 0) return;
        int n = matrix.length;
        if (n == 0) return;
        for (int i = 0; i < m / 2; i++) {
            int[] tmp = matrix[i];
            matrix[i] = matrix[m - i - 1];
            matrix[m - i - 1] = tmp;
        }
        for (int i = 0; i < m; i++)
            for (int j = i + 1; j < n; j++) {
                int tmp = matrix[i][j];
                matrix[i][j] = matrix[j][i];
                matrix[j][i] = tmp;
            }
    }