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] ]
1 class Solution { 2 public void transpose(int [][] matrix) { 3 int n = matrix.length; 4 for (int i = 0; i < n; ++i) { 5 for (int j = i + 1; j < n; ++j) { 6 int temp = matrix[i][j]; 7 matrix[i][j] = matrix[j][i]; 8 matrix[j][i] = temp; 9 } 10 } 11 } 12 13 public void reverse(int []matrix) { 14 int n = matrix.length; 15 for (int i = 0, j = n - 1; i < j; i++, j--) { 16 int temp = matrix[i]; 17 matrix[i] = matrix[j]; 18 matrix[j] = temp; 19 } 20 } 21 public void rotate(int[][] matrix) { 22 transpose(matrix); 23 for (int i = 0; i < matrix.length; ++i) { 24 reverse(matrix[i]); 25 } 26 } 27 }