【Leetcode】Rotate Image

【题目】

You are given an n x n 2D matrix representing an image.

Rotate the image by 90 degrees (clockwise).

【思路】

The idea was firstly transpose the matrix and then flip it symmetrically. For instance,

1  2  3
4  5  6
7  8  9

after transpose, it will be swap(matrix[i][j], matrix[j][i])

1  4  7
2  5  8
3  6  9

Then flip the matrix horizontally. (swap(matrix[i][j], matrix[i][matrix.length-1-j])

7  4  1
8  5  2
9  6  3

【代码】

public class Solution {
public void rotate(int[][] matrix) {
for(int i = 0; i<matrix.length; i++){
for(int j = i; j<matrix[0].length; j++){
int temp = 0;
temp = matrix[i][j];
matrix[i][j] = matrix[j][i];
matrix[j][i] = temp;
}
}
for(int i =0 ; i<matrix.length; i++){
for(int j = 0; j<matrix.length/2; j++){
int temp = 0;
temp = matrix[i][j];
matrix[i][j] = matrix[i][matrix.length-1-j];
matrix[i][matrix.length-1-j] = temp;
}
}
}
}