HW2_priority_queue

#include <cstdio>
#include <cstdlib>

struct Item
{
    int key;
    int priority;
};

struct PrQueue
{
    int size;
    Item* queue;
} queue;

void swap(Item &a, Item &b)
{
    Item t = a;
    a = b;
    b = t;
}

void siftup(Item * heap, int i)
{
    while (heap[i].priority < heap[(i - 1) / 2].priority)
    {
        swap(heap[i], heap[(i - 1) / 2]);
        i = (i - 1) / 2;
    }
}

void siftdown(Item * heap, int i, int n)
{
    int left = 0, right = 0, j = 0;
    while (2 * i + 1 < n)
    {
        left = 2 * i + 1;
        right = 2 * i + 2;
        j = left;
        if (right < n && heap[right].priority < heap[left].priority)
            j = right;
        if (heap[i].priority < heap[j].priority)
            return;
        swap(heap[i], heap[j]);
        i = j;
    }
}

void add(Item * heap, Item i, int &n)
{
    n++;
    heap[n - 1] = i;
    siftup(heap, n - 1);
}

int delete_min(Item *heap, int &n)
{
    int min = heap[0].key;
    heap[0] = heap[n - 1];
    n--;
    siftdown(heap, 0, n);
    return min;
}

int size(PrQueue name)
{
    return name.size;
}


int main()
{
    int n = 0;
    scanf("%d", &n);
    queue.queue = (Item*)malloc(n * sizeof(Item));
    queue.size = 0;
    for (int i = 0; i < n; i++)
    {
        scanf("%d", &queue.queue[i].key);
        scanf("%d", &queue.queue[i].priority);
        add(queue.queue, queue.queue[i], queue.size);
    }
    printf("%d\n", delete_min(queue.queue, queue.size));
    printf("%d\n", size(queue));
    free(queue.queue);
    return 0;
}