Data Structures | Queue | Question 1
Following is C like pseudo code of a function that takes a Queue as an argument, and uses a stack S to do processing.
void fun(Queue *Q){ Stack S; // Say it creates an empty stack S // Run while Q is not empty while (!isEmpty(Q)) { // deQueue an item from Q and push the dequeued item to S push(&S, deQueue(Q)); } // Run while Stack S is not empty while (!isEmpty(&S)) { // Pop an item from S and enqueue the poppped item to Q enQueue(Q, pop(&S)); }} |
What does the above function do in general?
(A) Removes the last from Q
(B) Keeps the Q same as it was before the call
(C) Makes Q empty
(D) Reverses the Q
Answer: (D)
Explanation: The function takes a queue Q as an argument. It dequeues all items of Q and pushes them to a stack S. Then pops all items of S and enqueues the items back to Q. Since stack is LIFO order, all items of queue are reversed.
