GFG PTOD | 20 Dec | Rotate by 90 degree

void rotateby90(vector<vector<int>>& mat) {
        // code here
        int n = mat.size();
        
        // transpose
        for(int i=0; i<n; i++) {
            for(int j=i+1; j<n; j++) {
                swap(mat[i][j], mat[j][i]);
            }
        }
        
        //Reverse
        for(int i=0; i<n; i++) {
            int top = 0, bottom = n-1;
            while(top <= bottom) {
                swap(mat[top][i], mat[bottom][i]);
                top++;
                bottom--;
            }
        }
    }