When working with queues in C++, you might have a scenario where you need to find the middle element of the queue. This could be useful, for example, when implementing a priority queue and you want to access the middle element for certain operations.

In this blog post, we will explore an efficient approach to find the middle element of a queue in C++. Let’s get started!

Approach

To find the middle element of a queue, we can use two additional queues: tempQueue and middleQueue. We will traverse the original queue and simultaneously enqueue the elements into the tempQueue. However, before enqueuing each element into tempQueue, we first check if tempQueue has already half of the elements of the original queue. If so, we enqueue the front element of tempQueue into middleQueue.

Here’s the step-by-step algorithm:

1. Create an empty queue called tempQueue and middleQueue.
2. Traverse the original queue:
   • Enqueue each element into tempQueue.
   • Check if tempQueue has already half of the elements of the original queue.
   • If so, enqueue the front element of tempQueue into middleQueue.
3. Finally, the front element of middleQueue will be the middle element of the original queue.

Implementation

#include <iostream>
#include <queue>

// Function to find the middle element of a queue
int findMiddleElement(std::queue<int>& q) {
    std::queue<int> tempQueue, middleQueue;
    int count = 0;
    int middleElement = 0;

    // Traverse the original queue
    while (!q.empty()) {
        // Enqueue each element into the tempQueue
        tempQueue.push(q.front());
        q.pop();

        count++;
        // Check if tempQueue has already half of the elements of the original queue
        if (count % 2 == 0) {
            // Enqueue the front element of tempQueue into middleQueue
            middleQueue.push(tempQueue.front());
            tempQueue.pop();
        }
    }

    // Get the middle element from middleQueue
    if (!middleQueue.empty()) {
        middleElement = middleQueue.front();
    }

    return middleElement;
}

int main() {
    std::queue<int> q;
    q.push(10);
    q.push(20);
    q.push(30);
    q.push(40);
    q.push(50);

    int middleElement = findMiddleElement(q);

    std::cout << "Middle element of the queue: " << middleElement << std::endl;

    return 0;
}

Conclusion

In this blog post, we learned how to find the middle element of a queue in C++ using an efficient approach. By leveraging two additional queues, we can easily access the middle element of a queue without going through the entire queue.

Using this approach, you can now incorporate finding the middle element of a queue in your C++ programs efficiently.