RotateImage.java

package medium;
import static util.Utils.*;
/**
 * 
 * ClassName: RotateImage
 * @author chenyiAlone  
 * Create Time: 2018/12/26 17:34:50
 * Description: No.48
 * 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]
    ]
 */
public class RotateImage {
    public void rotate(int[][] matrix) {
        int m = matrix.length;
        int n = matrix[0].length;
//        System.out.println(m + " " + n);
        int[][] nmat = new int[n][m];
        for (int i = 0; i < n; i++) {
            for (int j = 0; j < n; j++) {
                nmat[i][j] = matrix[i][j];    
            }
        }
        for (int i = 0; i < n; i++) {
            for (int j = 0; j < n; j++) {
                matrix[i][j] = nmat[n - j - 1][i];    
            }
            
        }
        matrix = nmat;
    }
    public static void main(String[] args) {
        int[][] matrix = { {1, 2, 3},
                           {4, 5, 6},
                           {7, 8, 9}
                           };
        System.out.println("old Image:");
        for (int[] t : matrix) {
            printArray(t);
        }
        new RotateImage().rotate(matrix);
        System.out.println("new Image:");
        for (int[] t : matrix) {
            printArray(t);
        }
    }
}