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] ]
此題旋轉90度,採用兩步走,先中心翻轉後據y翻轉。Accepted代碼如下:
class Solution {
public void rotate(int[][] matrix) {
for (int i = 0; i < matrix.length; i++) {
for (int j = 0; j < i; 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[0].length - 1 - j];
matrix[i][matrix[0].length - 1 - j] = tmp;
}
}
}
}