Matrix Rotation (In Memory)

 Thinking Process:

1. We have to iterate over the columns of the matrix and keep adding elements in a queue starting from the last row of each column.
2. Now, simply empty the queue into the matrix.
   NOTE: By adding the elements into the queue in the above fashion, we are creating a queue which will effectively produce a rotated image (if updated in the matrix in a row-wise manner).

Now if we look at the image closely, we will observe that each column (from bottom to up) becomes a row after rotation.
This is the sequence we are creating in the queue.

public void rotate(int[][] matrix) {
        Queue<Integer> q = new LinkedList<>();
        for(int j=0;j<matrix[0].length;j++){   //iterate over columns 
            for(int i=matrix.length-1;i>=0;i--){  //last row to 0th row
                q.add(matrix[i][j]);
            }
        }
        while(!q.isEmpty()){
            for(int i=0;i<matrix.length;i++){
                for(int j=0;j<matrix[0].length;j++)
                    matrix[i][j] = q.poll();
            }
        }
    }