Instead of dividing the matrix by diagonal, I divide it into 4 pieces by central axes. Then do the transform:

```
class Solution {
public:
void rotate(vector<vector<int> > &matrix) {
int n = matrix.size();
for (int i = 0; i < (n + 1) / 2; i++)
{
for (int j = 0; j < n / 2; j++)
{
int temp = matrix[i][j];
matrix[i][j] = matrix[n - 1 - j][i];
matrix[n - 1 - j][i] = matrix[n - 1 - i][n - 1 - j];
matrix[n - 1 - i][n - 1 - j] = matrix[j][n - 1 - i];
matrix[j][n - 1 - i] = temp;
}
}
}
};
```