Leetcode48. Rotate image

subject ：

Given a n × n Two dimensional matrix representation of an image .

Rotate image clockwise 90 degree .

explain ：

You must be there. In situ Rotated image , This means that you need to modify the input two-dimensional matrix directly . Please do not Use another matrix to rotate the image .

Example 1:

 Given  matrix =
[
    [1,2,3],
    [4,5,6],
    [7,8,9]
],
​
 In situ rotation input matrix , Turn it into :
[
    [7,4,1],
    [8,5,2],
    [9,6,3]
]

Example 2:

 Given  matrix =
[
    [ 5, 1, 9,11],
    [ 2, 4, 8,10],
    [13, 3, 6, 7],
    [15,14,12,16]
],
​
 In situ rotation input matrix , Turn it into :
[
    [15,13, 2, 5],
    [14, 3, 4, 1],
    [12, 6, 8, 9],
    [16, 7,10,11]
]

 

 

   // Rotated image 
    public static int[][] _124_solution(int[][] matrix) {
        // First from [0, 0]  To  [n-1, n-1] Diagonals , Flip 
        for (int i = 1; i < matrix.length; i++) {
            for (int j = 0; j < i; j++) {
                swapMatrix(matrix, i, j, j, i);
            }
        }
​
        // Then cut the line vertically from the middle , Flip each row 
        for (int i = 0; i < matrix.length; i++) {
            for (int j = 0; j < matrix.length / 2; j++) {
                swapMatrix(matrix, i, j, i, matrix.length - 1 - j);
            }
        }
​
        return matrix;
    }
​
    private static void swapMatrix(int[][] matrix, int i, int j, int a, int b) {
        int tmp = matrix[i][j];
        matrix[i][j] = matrix[a][b];
        matrix[a][b] = tmp;
    }