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Priority Queue Implementation in C ++

I am trying to implement a queue using a circular array. My code should be able to remove the lowest number from the queue. I created a test code that should output 1 2 3 4 5 since the lowest values ​​are deleted, but my actual result is 3 2 1 8 7. I'm not sure if my problem is that my code to find the lowest value is incorrect or there is a problem with how I encode the actual queue. I suspect both, but I would appreciate any suggestions or tips for finding problems in my code.

#include <iostream>
using namespace std;

class priorityQueue
{
private:
    int front;
    int rear;
    int size;
    int *array;

public:
    priorityQueue();
    ~priorityQueue();
    void insert(int x);
    //remove and return the smallest item currently in the priority queue
    int extractMin();
    bool empty();
};

priorityQueue::priorityQueue()
{
    front = rear = -1;
    size = 10;
    array = new int[size];
}

priorityQueue::~priorityQueue()
{
    delete[] array;
}

void priorityQueue::insert(int x)
{
    //if queue is full
    if ( (rear + 1)% size == front ){
        return;
    }

    //else if queue is empty
    else if ( empty() ){
        rear = front = 0;
    }

    else
    {
        rear = (rear + 1) % size;
    }

    array[rear] = x;
}

//extract and return smallest value in queue
int priorityQueue::extractMin()
{
    int minValue = array[front];

    if ( empty() ){
        return -1;
    }

    else if (front == rear){
        front = rear = -1;
        }

    else
    {
        front = (front + 1) % size;
    }

    //find smallest value
    for (int i = front; i <= rear; i++){
        if (array[i] < minValue)
            minValue = array[i];
    }

    //return smallest value
    return array[front];
}

bool priorityQueue::empty()
{
    if ( (front == -1) && (rear == -1) )
        return true;
    else
        return false;
}

int main()
{
    priorityQueue myqueue;

    myqueue.insert(4);
    myqueue.insert(3);
    myqueue.insert(2);
    myqueue.insert(1);

    cout << myqueue.extractMin() << endl;
    cout << myqueue.extractMin() << endl;

    myqueue.insert(8);
    myqueue.insert(7);
    myqueue.insert(6);
    myqueue.insert(5);

    cout << myqueue.extractMin() << endl;
    cout << myqueue.extractMin() << endl;
    cout << myqueue.extractMin() << endl;

    system("pause");
    return 0;
}
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2 answers

You will find the smallest value, however it is not the value that you return when you extract min:

//find smallest value
for (int i = front; i <= rear; i++){
    if (array[i] < minValue)
        minValue = array[i];
}

//return smallest value
return array[front]; //Not equal to the smallest value

, , , , .

, , , :

int minIndex = front;

//find smallest value
for (int i = front; i <= rear; i++){
    if (array[i] < minValue)
    {
        minIndex = i;
        minValue = array[i];
    }
}

array[minIndex] = array[front];

//return smallest value
return minValue;

, , , , .

int index = rear;

for(int i = front ; i <= rear ; i++)
{
    if(x < array[i])
    {
        for(int j = rear ; j >= i ; j--)
        {
            array[j] = array[j-1];
        }
        index = i;
        break;
    }
}

array[index] = x;

, , , . , .

else
{
    front = (front+1) % size;
}

extractmin - :

//extract and return smallest value in queue
int priorityQueue::extractMin()
{
    //Handle circulation.

    //return smallest value
    return array[front++];
}
+1

, :

//return smallest value
    return array[front];

,

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+1

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