Rotate Image

You are given an n x n 2D matrix representing an image, rotate the image by 90 degrees (clockwise).

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:

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

Example 2:

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

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

Solution

class Solution {

public void rotate(int[][] matrix) {

int n = matrix.length;

for (int i = 0; i < (n + 1) / 2; i++) {

for (int j = 0; j < n / 2; j++) {

int temp = matrix[n - 1 - j][i];

matrix[n - 1 - j][i] = matrix[n - 1 - i][n - j - 1];

matrix[n - 1 - i][n - j - 1] = matrix[j][n - 1 - i];

matrix[j][n - 1 - i] = matrix[i][j];

matrix[i][j] = temp;

}

}

}

}