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

typedef struct node {
    void *content;
    struct node *next;
}Node;

typedef struct queue {
    Node *first;
    Node *last;
    size_t w;
}Queue;

Queue *new_queue(size_t w) {
    Queue *q = malloc(sizeof(Queue));
    q->first = NULL;
    q->last = NULL;
    q->w = w;
    return q;
}

bool is_empty(Queue *q) {
    return !q->first;
}

void enqueue(void *content, Queue *q) {
    Node *n = malloc(sizeof(Node));
    n->content = content;
    n->next = NULL;
    if (is_empty(q))
        q->first = n;
    else
        q->last->next = n;
    q->last = n;
}

void *dequeue(Queue *q) {
    if (is_empty(q))
        return NULL;
    void *r = q->first->content;
    Node *n = q->first;
    q->first = q->first->next;
    free(n);
    if (is_empty(q))
        q->last = NULL;
    return r;
}

void destroy(Queue *q) {
    while (!is_empty(q)) {
        free(dequeue(q));
    }
    free(q);
}

int main() {
    Queue *q = new_queue(sizeof(int));
    int *a = malloc(sizeof(int));
    int *b = malloc(sizeof(int));
    int *c = malloc(sizeof(int));
    int *d = malloc(sizeof(int));
    *a=1;
    *b=2;
    *c=3;
    *d=-1;
    enqueue(a, q);
    printf("%d\n", *((int*)dequeue(q)));
    enqueue(b, q);
    enqueue(c, q);
    enqueue(d, q);
    while(!is_empty(q)) {
        printf("%d\n", *((int*)dequeue(q)));
    }
    destroy(q);
    return 0;

}