queue.go
func (queue *queue) PeekBack() interface{} {
	if queue.size == 0 {
		return nil
	}

	return queue.elements[(queue.end-1)%int64(queue.cap)]
}
func (queue *queue) PeekBack() interface{} {
	if queue.size == 0 {
		return nil
	}

	return queue.elements[(queue.end-1)%int64(queue.cap)]
}
func ( queue * queue ) PeekBack ( ) interface { } { if queue . size == 0 { return nil } return queue . elements [ ( queue . end - 1 ) % int64 ( queue . cap ) ] }
// PeekBack returns the element at the back of the queue.
PeekBack returns the element at the back of the queue .