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Algorithms Quiz | SP Contest 3 | Question 4

  • Last Updated : 25 Jul, 2018
Geek Week

What does the below function do in general?

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));

(A) Removes the last element from the queue, Q
(B) Keeps the queue, Q same as it was before the call
(C) Makes queue Q empty
(D) Reverses the queue 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 the queue are reversed.

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