解决思路

    public void rotate(int[][] matrix) {
         int n = matrix.length;
        // 转置矩阵
        for (int i = 0; i < n; i++) {
              for (int j = i; j < n; j++) {
                int tmp = matrix[j][i];
                matrix[j][i] = matrix[i][j];
                matrix[i][j] = tmp;
              }
        }
        //每一行进行反转
         // reverse each row
        for (int i = 0; i < n; i++) {
              for (int j = 0; j < n / 2; j++) {
                int tmp = matrix[i][j];
                matrix[i][j] = matrix[i][n - j - 1];
                matrix[i][n - j - 1] = tmp;
              }
        }
    }