Title description:
Give you an image represented by an N × N matrix, where each pixel is 4 bytes in size. Please design an algorithm to rotate the image by 90 degrees.
Can it be done without taking up additional memory space?
Example 1:
Given matrix =
[
[1,2,3],
[4,5,6],
[7,8,9]
],
Rotate the input matrix in place so that it becomes:
[
[7,4,1],
[8,5,2],
[9,6,3]
]
Example 2:
Given matrix =
[
[ 5, 1, 9,11],
[ 2, 4, 8,10],
[13, 3, 6, 7],
[15,14,12,16]
],
Rotate the input matrix in place so that it becomes:
[
[15,13, 2, 5],
[14, 3, 4, 1],
[12, 6, 8, 9],
[16, 7,10,11]
]
code show as below:
class Solution {
public void rotate(int[][] matrix) {
int n = matrix.length;
// 水平翻转
for (int i = 0; i < n / 2; ++i) {
for (int j = 0; j < n; ++j) {
int temp = matrix[i][j];
matrix[i][j] = matrix[n - i - 1][j];
matrix[n - i - 1][j] = temp;
}
}
// 主对角线翻转
for (int i = 0; i < n; ++i) {
for (int j = 0; j < i; ++j) {
int temp = matrix[i][j];
matrix[i][j] = matrix[j][i];
matrix[j][i] = temp;
}
}
}
}
Results of the:
