Rotating image algorithm: given an n×n two-dimensional matrix, rotate it clockwise by 90°
For example:
Enter:
[1, 2, 3]
[4, 5, 6]
[7, 8, 9]

Output:
[7, 4, 1]
[8, 5, 2]
[9, 6, 3]

enter:
[1, 2, 3, 4]
[5, 6, 7, 8]
[9, 10, 11, 12]
[13, 14, 15, 16]
output:
[13, 9, 5, 1]
[14, 10, 6, 2]
[15, 11, 7, 3]
[16, 12, 8, 4]

Thinking analysis:
1. Obviously use a two-dimensional array to solve the problem. Here we use a matrix of 1 to 9 total 9 digits as an example to traverse
2. First, in the input, the positions of 123 in the two-dimensional array are:[0][0],[0][1],[0][2]
3. Secondly in the output, the positions of 123 in the two-dimensional array are:[0][2],[1][2],[2][2]
4. When the array traverses the outer loop i=0, temp[j][3-0-i]=matrix[i][j], j takes the value 0~2, and determines 3 Number
5. When the array traverses the outer loop i=1, temp[j][3-0-i]=matrix[i][j], j takes the value 0~2, and determines 3 Number
6. When the array traverses the outer loop i=2, temp[j][3-0-i]=matrix[i][j], j takes the value 0~2, and determines 3 Number
7. The law will come out

The code sheet is as follows

 public static int[][] rotate(int[][] matrix) {
        int len=matrix.length;
        int[][] temp = new int[len][len];
        for (int i = 0; i < len; i++) {
            for (int j = 0; j < len; j++) {
                temp[j][len - i - 1] = matrix[i][j];
            }
        }
        return temp;
    }

start testing:

 public static void main(String[] args) {
        int[][] matrix0 = {
                {1, 2, 3},
                {4, 5, 6},
                {7, 8, 9}};
        int[][] matrix = {
                {1, 2, 3, 4},
                {5, 6, 7, 8},
                {9, 10, 11, 12},
                {13, 14, 15, 16}};
        print(matrix);
        System.out.println("-----------");
        print(rotate(matrix));

    }

    public static void print(int[][] matrix) {
        for (int i = 0; i < matrix.length; i++) {
            System.out.println(Arrays.toString(matrix[i]));
        }
    }

Output:

[1, 2, 3, 4]
[5, 6, 7, 8]
[9, 10, 11, 12]
[13, 14, 15, 16]
-----------
[13, 9, 5, 1]
[14, 10, 6, 2]
[15, 11, 7, 3]
[16, 12, 8, 4]