sda priority q

#include <stdio.h>
#include <stdlib.h>

typedef struct Node {
    int data;
    struct Node* nxt;
} Node;

Node* newNode(int data, Node *nxt) {
    Node* node = (Node*)malloc(sizeof(Node));
    if (node == NULL) {
        perror("");
        exit(1);
    }
    node->data = data;
    node->nxt = nxt;
    return node;
}

typedef struct {
    Node* first;
    Node* last;
} PQueue;

int extract(PQueue pq) {
    if (pq.last == NULL) {
        perror("extract error");
        exit(1);
    }
    return pq.last->data;
}

void insert(PQueue *pq, int data) {
    if (pq->first == NULL) {
        pq->first = pq->last = newNode(data, NULL);
        return;
    }
    if (pq->first->data > data) {
        pq->first = newNode(data, pq->first);
        return;
    }
    Node* aux = pq->first;
    while (aux->nxt != NULL) {
        if (aux->data < data && data < aux->nxt->data) {
            aux->nxt = newNode(data, aux->nxt);
            return;
        }
        aux = aux->nxt;
    }
    pq->last->nxt = newNode(data, NULL);
}

void pop(PQueue *pq) {
    Node* aux = pq->first;
    while (aux->nxt != pq->last) {
        aux = aux->nxt;
    }
    free(pq->last);
    pq->last = aux;

}

void display(const PQueue *const pq) {
    for (Node* node = pq->first; node != NULL; node = node->nxt) {
        printf("%d ", node->data);
    }
    puts("");
}

void initPq(PQueue* pq) {
    pq->first = pq->last = NULL;
}

void freePQ(PQueue* pq) {
    Node* curr = pq->first;
    Node* nxt = NULL;
    while (curr) {
        nxt = curr->nxt;
        free(curr);
        curr = nxt;
    }
}

int main(void) {
    PQueue pq;
    initPq(&pq);
    insert(&pq, 12);
    insert(&pq, 4);
    insert(&pq, 1);
    insert(&pq, 3);
    insert(&pq, 5);
    insert(&pq, 45);
    insert(&pq, 40);
    display(&pq);
    freePQ(&pq);
    return 0;
}