In this blog post, we’ll explore how to reverse a queue in C++. A queue is a data structure that follows the First-In-First-Out (FIFO) principle, which means that the element that has been in the queue the longest is the first one to be removed. Reversing a queue involves changing the order of its elements so that the last element becomes the first, and vice versa.

Let’s dive into the code and see how we can reverse a queue.

Implementation

To reverse a queue, we can make use of an additional stack data structure. By pushing all elements from the queue onto the stack and then popping them back into the queue, we can effectively reverse the order of the elements.

Here’s an example implementation in C++:

#include <iostream>
#include <queue>
#include <stack>

void reverseQueue(std::queue<int>& q) {
    std::stack<int> s;

    // Push all elements from the queue onto the stack
    while (!q.empty()) {
        s.push(q.front());
        q.pop();
    }

    // Pop elements from the stack and push them back into the queue
    while (!s.empty()) {
        q.push(s.top());
        s.pop();
    }
}

int main() {
    std::queue<int> q;

    // Enqueue elements into the queue
    q.push(1);
    q.push(2);
    q.push(3);
    q.push(4);
    q.push(5);

    // Reverse the queue
    reverseQueue(q);

    // Dequeue and print the reversed queue
    while (!q.empty()) {
        std::cout << q.front() << " ";
        q.pop();
    }

    return 0;
}

In this example, we define a reverseQueue function that takes a reference to a queue as a parameter. Inside the function, we create a stack and push all elements from the queue onto the stack using a while loop. Then, we pop elements from the stack and push them back into the queue in reverse order. Finally, in the main function, we enqueue elements into the queue, reverse the queue using the reverseQueue function, and dequeue and print the reversed queue.

Conclusion

Reversing a queue in C++ can be done by utilizing an additional stack. By pushing the elements from the queue onto the stack and then popping them back into the queue, we can effectively reverse the order of the elements. The example code discussed in this blog post illustrates this approach. Try it out and experiment with different scenarios to deepen your understanding of reversing queues.

I hope you found this blog post helpful! If you have any questions or comments, please feel free to reach out.

#C++ #Queue #DataStructure