C++ Queue Exercises: Sort the elements of a queue

C++ Queue: Exercise-3 with Solution

Write a C++ program to sort the elements of a queue.

Sample Solution:

C Code:

#include <iostream>
#include <stack>

using namespace std;

const int MAX_SIZE = 100;

class Queue {
private:
  int front; // Front index of the queue
  int rear; // Rear index of the queue
  int arr[MAX_SIZE]; // Array to store elements

public:
  Queue() {
    front = -1; // Initialize front index to -1
    rear = -1; // Initialize rear index to -1
  }

  bool isFull() {
    return (rear == MAX_SIZE - 1); // Check if the queue is full
  }

  bool isEmpty() {
    return (front == -1 && rear == -1); // Check if the queue is empty
  }

  void enqueue(int x) {
    if (isFull()) {
      cout << "Error: Queue is full" << endl; // Display error message if queue is full
      return;
    }
    if (isEmpty()) {
      front = 0;
      rear = 0;
    } else {
      rear++;
    }
    arr[rear] = x; // Insert the element at the rear index
  }

  void dequeue() {
    if (isEmpty()) {
      cout << "Error: Queue is empty" << endl; // Display error message if queue is empty
      return;
    }
    if (front == rear) {
      front = -1;
      rear = -1;
    } else {
      front++;
    }
  }

  int peek() {
    if (isEmpty()) {
      cout << "Error: Queue is empty" << endl; // Display error message if queue is empty
      return -1;
    }
    return arr[front]; // Return the element at the front of the queue
  }

  void display() {
    if (isEmpty()) {
      cout << "Error: Queue is empty" << endl; // Display error message if queue is empty
      return;
    }
    cout << "Queue elements are: ";
    for (int i = front; i <= rear; i++) {
      cout << arr[i] << " "; // Display all elements in the queue
    }
    cout << endl;
  }

  // Function to sort the elements of the queue in ascending order
  void sortQueue(Queue & q) {
    if (q.isEmpty()) {
      cout << "Error: Queue is empty" << endl; // Display error message if queue is empty
      return;
    }
    int n = q.rear - q.front + 1; // Calculate the number of elements in the queue
    for (int i = 0; i < n - 1; i++) {
      int minIndex = i;
      int minValue = q.arr[q.front + i];
      // Find the index and value of the minimum element in the unsorted portion of the queue
      for (int j = i + 1; j < n; j++) {
        if (q.arr[q.front + j] < minValue) {
          minIndex = j;
          minValue = q.arr[q.front + j];
        }
      }
      // Shift elements to the right to make space for the minimum element
      for (int j = minIndex; j > i; j--) {
        q.arr[q.front + j] = q.arr[q.front + j - 1];
      }
      q.arr[q.front + i] = minValue; // Place the minimum value in the correct sorted position
    }
  }
};

int main() {
  cout << "Initialize a Queue." << endl;
  Queue q;
  cout << "\nInsert some elements into the queue:" << endl;
  q.enqueue(1);
  q.enqueue(5);
  q.enqueue(3);
  q.enqueue(6);
  q.enqueue(2);
  q.enqueue(0);
  q.display();
  q.sortQueue(q); // Sort the elements of the queue
  cout << "\nSort the above Queue elements:\n";
  q.display();
  cout << "\nInput two more elements into the queue:" << endl;
  q.enqueue(-1);
  q.enqueue(4);
  q.display();
  q.sortQueue(q); // Sort the elements of the queue
  cout << "\nSort the above Queue elements:\n";
  q.display();
  return 0;
}

Sample Output:

Initialize a Queue.

Insert some elements into the queue:
Queue elements are: 1 5 3 6 2 0

Sort the above Queue elements:
Queue elements are: 0 1 2 3 5 6

Input two more elements into the queue:
Queue elements are: 0 1 2 3 5 6 -1 4

Sort the above Queue elements:
Queue elements are: -1 0 1 2 3 4 5 6

Flowchart:

CPP Code Editor:

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Previous C++ Exercise: Reverse the elements of a queue.
Next C++ Exercise: Find the sum of all elements of a queue.