In this article, we will see how to reverse a queue using a stack.
Steps to Reverse Queue using Stack
- Pop the queue and push all the elements of the queue to stack.
- Pop the stack and push all the elements back to the queue.
- The queue is now reversed.
Example,
Program
#include<iostream>
#include<stack>
#include<queue>
using namespace std;
void ReverseQueueUsingStack(queue<int>& q)
{
stack<int> s;
// push all elements of queue to stack
while (!q.empty())
{
s.push(q.front());
q.pop();
}
// push all elements of the stack back to queue
while (!s.empty())
{
q.push(s.top());
s.pop();
}
}
int main()
{
int n, x;
queue<int> q;
cout << "Enter number of elements you want to Push to Queue: ";
cin >> n;
cout<<"Enter Queue Elements"<<endl;
for (int i = 0; i < n; ++i)
{
cin >> x;
q.push(x);
}
cout << "Front element of Queue: " << q.front() << endl;
ReverseQueueUsingStack(q);
cout << "Front element of Queue after Reverse: " << q.front() << endl;
}
Output
Enter number of elements you want to Push to Queue: 4
Enter Queue Elements
1 2 3 4
Front element of Queue: 1
Front element of Queue after Reverse: 4Read