旋转一个矩阵

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.

思路：转置在中心对称线交换

 

class Solution {
public:
void rotate(vector<vector<int>>& matrix) {
int row=matrix.size();
int col=matrix[0].size();
for(int i=0;i<row;++i){
for(int j=0;j<i;++j){
swap(matrix[i][j],matrix[j][i]);
}
}
for(int i=0;i<row;++i){
int l=0,r=row-1;
while(l<r){
swap(matrix[i][l],matrix[i][r]);
l++;r--;
}
}
}
};