题目要求:
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.
翻转一个二维数组90度。(数组大小为N*N)
例如,输入:
matrix =
[
[1,2,3],
[4,5,6],
[7,8,9]
]
输出:
[
[7,4,1],
[8,5,2],
[9,6,3]
]
输入:
matrix =
[
[ 5, 1, 9,11],
[ 2, 4, 8,10],
[13, 3, 6, 7],
[15,14,12,16]
]
输出:
[
[15,13, 2, 5],
[14, 3, 4, 1],
[12, 6, 8, 9],
[16, 7,10,11]
]
思路:
如图,数组翻转90度,只需要以蓝色三角内,每个数字为基准,进行旋转,以一个数字为基准,移动4次,即上图中4个箭头的指向。
代码如下:
class Solution {
public void rotate(int[][] matrix) {
int matrixLength=matrix.length;
for (int i = 0; i < matrixLength/2; i++) {
for (int j = i; j <matrixLength-i-1 ; j++) {
int tmpValue1=matrix[i][j];
matrix[i][j]=matrix[matrixLength-1-j][i];
matrix[matrixLength-1-j][i]=matrix[matrixLength-1-i][matrixLength-1-j];
matrix[matrixLength-1-i][matrixLength-1-j]=matrix[j][matrixLength-1-i];
matrix[j][matrixLength-1-i]=tmpValue1;
}
}
}
}
结果: