reverseQueue.cpp

#include <bits/stdc++.h>

using namespace std;

/**
 *  Reverse Queue
 *  -   You have been given a queue that can store integers as the data.
 *      You are required to write a function that reverses the populated
 *      queue itself without using any other data structures.
 *
 *  Input Format:
 *      The first list of input contains an integer 't' denoting the number of
 *      test cases/queries to be run.
 *      Then the test cases follow.
 *      The first line input for each test case/query contains an integer N,
 *      denoting the total number of elements in the queue.
 *      The second line of input contains N integers separated by a single space,
 *      representing the order in which the elements are enqueued into the queue.
 *  Output Format:
 *      For each test case/query, the only line of output prints the order in
 *      which the queue elements are dequeued, all of them separated by a single space.
 *      Output for every test case/query will be printed on a new line.
 *
 *  Constraints:
 *      1 <= t <= 100
 *      1 <= N <= 10^4
 *      -2^31 <= data <= 2^31 - 1
 *
 *  Time Limit: 1sec
 *
 *  Sample Input 1:
 *      1
 *      6
 *      1 2 3 4 5 10
 *  Note:
 *      Here, 1 is at the front and 10 is at the rear of the queue.
 *  Sample Output 1:
 *      10 5 4 3 2 1
 *
 *  Sample Input 2:
 *      2
 *      5
 *      2 8 15 1 10
 *      3
 *      10 20 30
 *  Sample Output 2:
 *      10 1 15 8 2
 *      30 20 10
 */
void reverseQueue(queue<int> &input)
{
    if (input.empty())
    {
        return;
    }
    int temp = input.front();
    input.pop();
    reverseQueue(input);
    input.push(temp);
}
void assignment1()
{
    int t;
    cin >> t;
    while (t--)
    {
        queue<int> q;
        int size;
        cin >> size;
        for (int i = 0, val; i < size; i++)
        {
            cin >> val;
            q.push(val);
        }
        reverseQueue(q);
        while (!q.empty())
        {
            cout << q.front() << " ";
            q.pop();
        }
        cout << "\n";
    }
}