Reverse First K elements of Queue.cpp

/* 
    Solution by Rahul Surana
    
    ***********************************************************


Given an integer K and a queue of integers, we need to reverse the order of the first K elements of the queue, leaving the other elements in the same relative order.

Only following standard operations are allowed on queue.

enqueue(x) : Add an item x to rear of queue
dequeue() : Remove an item from front of queue
size() : Returns number of elements in queue.
front() : Finds front item.



    ***********************************************************
*/


// { Driver Code Starts
// Initial Template for C++

#include <bits/stdc++.h>
using namespace std;
queue<int> modifyQueue(queue<int> q, int k);
int main() {
    int t;
    cin >> t;
    while (t-- > 0) {
        int n, k;
        cin >> n >> k;
        queue<int> q;
        while (n-- > 0) {
            int a;
            cin >> a;
            q.push(a);
        }
        queue<int> ans = modifyQueue(q, k);
        while (!ans.empty()) {
            int a = ans.front();
            ans.pop();
            cout << a << " ";
        }
        cout << endl;
    }
}// } Driver Code Ends


// User function Template for C++

// Function to reverse first k elements of a queue.
queue<int> modifyQueue(queue<int> q, int k) {
    stack<int> s;
    int i = 0;
    while(i < k){
        s.push(q.front());
        q.pop();
        i++;
    }
    int x = q.size();
    while(!s.empty()) {
        q.push(s.top());
        s.pop();
    }
    while(x>0){
        q.push(q.front());
        q.pop();
        x--;
    }
    return q;
}