[3]48. Rotate Image(Java)

You are given an n x n 2D matrix representing an image.

Rotate the image by 90 degrees (clockwise).

Note:
You have to rotate the image in-place, which means you have to modify the input 2D matrix directly. DO NOT allocate another 2D matrix and do the rotation.

Example 1:

Given input matrix = [  [1,2,3],  [4,5,6],  [7,8,9]],rotate the input matrix in-place such that it becomes:[  [7,4,1],  [8,5,2],  [9,6,3]]

Example 2:

Given input matrix =[  [ 5, 1, 9,11],  [ 2, 4, 8,10],  [13, 3, 6, 7],  [15,14,12,16]], rotate the input matrix in-place such that it becomes:[  [15,13, 2, 5],  [14, 3, 4, 1],  [12, 6, 8, 9],  [16, 7,10,11]]

clockwise rotate ( Java ) :

/*    1  2  3                 4  5  6    7  8  9    swap(matrix[i][j], matrix[j][i])    1  4  7    2  5  8    3  6  9    swap(matrix[i][j], matrix[i][matrix.length-1-j])    7  4  1    8  5  2    9  6  3*/class Solution {    public void rotate(int[][] matrix) {        for (int i = 0; i < matrix.length; i ++) {            for (int j = i + 1; j < matrix[0].length; j ++) {                int tmp = matrix[i][j];                matrix[i][j] = matrix[j][i];                matrix[j][i] = tmp;            }        }        for (int i = 0; i < matrix.length; i ++) {            for (int j = 0; j < matrix[0].length / 2; j ++) {                int tmp = matrix[i][j];                matrix[i][j] = matrix[i][matrix.length - 1 - j];                matrix[i][matrix.length - 1 - j] = tmp;            }        }    }}

/* * clockwise rotate * first reverse up to down, then swap the symmetry  * 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 * swap(matrix[i][j], matrix[matrix.length - 1 - i][j]) * swap(matrix[i][j], matrix[j][i]) */class Solution {    public void rotate(int[][] matrix) {        for (int j = 0; j < matrix.length; j ++) {                for (int i = 0; i < matrix[0].length / 2; i ++) {                    int tmp = matrix[i][j];                    matrix[i][j] = matrix[matrix.length - 1 - i][j];                    matrix[matrix.length - 1 - i][j] = tmp;                }            }        for (int i = 0; i < matrix.length; i ++) {            for (int j = i + 1; j < matrix[0].length; j ++) {                int tmp = matrix[i][j];                matrix[i][j] = matrix[j][i];                matrix[j][i] = tmp;            }        }    }}

clockwise rotate ( C++ ) :

/* * clockwise rotate * first reverse up to down, then swap the symmetry  * 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*/void rotate(vector<vector<int> > &matrix) {    reverse(matrix.begin(), matrix.end());    for (int i = 0; i < matrix.size(); ++i) {        for (int j = i + 1; j < matrix[i].size(); ++j)            swap(matrix[i][j], matrix[j][i]);    }}

anticlockwise rotate( C++ ) :

/* * anticlockwise rotate * first reverse left to right, then swap the symmetry * 1 2 3     3 2 1     3 6 9 * 4 5 6  => 6 5 4  => 2 5 8 * 7 8 9     9 8 7     1 4 7*/void anti_rotate(vector<vector<int> > &matrix) {    for (auto vi : matrix) reverse(vi.begin(), vi.end());    for (int i = 0; i < matrix.size(); ++i) {        for (int j = i + 1; j < matrix[i].size(); ++j)            swap(matrix[i][j], matrix[j][i]);    }}