You are given an n x n 2D matrix representing an image, rotate the image by 90 degrees (clockwise).
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.
Solution
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class Solution {
public:
void rotate(vector<vector<int>>& matrix) {
int row = matrix.size(), col = matrix[0].size();
// transpose
for(int i=0;i<row;i++){
for(int j=i;j<col;j++){
swap(matrix[i][j], matrix[j][i]);
}
}
for(int i=0;i<row;i++){
int left=0, right=col-1;
while(left<right){
swap(matrix[i][left], matrix[i][right]);
left++;right--;
}
}
}
};
