Day 21.1.txt

48. 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]]
Example 3:

Input: matrix = [[1]]
Output: [[1]]
Example 4:

Input: matrix = [[1,2],[3,4]]
Output: [[3,1],[4,2]]
 

Constraints:

matrix.length == n
matrix[i].length == n
1 <= n <= 20
-1000 <= matrix[i][j] <= 1000



class Solution {
    public void rotate(int[][] m) {
        int i,j,d;
        for(i=0;i<m.length/2;i++)
        {
            for(j=i;j<m.length-i-1;j++)
            {
                d=m[i][j];
                m[i][j]=m[m.length-j-1][i];
                m[m.length-j-1][i]=m[m.length-i-1][m.length-1-j];
                m[m.length-1-i][m.length-1-j]=m[j][m.length-i-1];
                m[j][m.length-i-1]=d;
            }
        }
    }
}