Dynamic queue implementation - School HW

dynamic_queue.c

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

struct queue_node
{
    char x;
    struct queue_node *next;
};

struct queue
{
    struct queue_node *head;
    struct queue_node *tail;
};

typedef struct queue q_t;
typedef struct queue_node node_t;

int enqueue(q_t *queue, char val)
{
    node_t *new = calloc(1, sizeof(node_t));
    if (!new)
        return 1;

    new->x = val;
    new->next = 0;
    if (!queue->tail)
        queue->tail = new;
    else
        queue->head->next = new;
    queue->head = new;
    return 0;
}

int dequeue(char *out, q_t *queue)
{
    if (!queue->tail)
        return 1;

    *out = queue->tail->x;
    node_t *res = queue->tail;
    queue->tail = queue->tail->next;
    free(res);
    return 0;
}

void print_queue(q_t *queue)
{
    node_t *current = queue->tail;
    printf("The queue is:\n");
    while (current)
    {
        printf("%c --> ", current->x);
        current = current->next;
    }

    printf("NULL\n\n");
}

void init(q_t *queue)
{
    queue->head = queue->tail = 0;
}

int main()
{
    q_t *queue = malloc(sizeof(q_t));
    init(queue);
    char item;
    int choice;
    int res;

    printf("%s\n%s\n%s\n%s\n",
           "Enter your choice: ",
           "    1 to add an item to the queue",
           "    2 to remove an item from the queue",
           "    3 to end"
    );

    while (choice != 3)
    {
        printf("? ");
        scanf("%d", &choice);

        switch (choice)
        {
            case 1:
                printf("Enter a character: ");
                scanf("\n%c", &item);
                enqueue(queue, item);
                break;

            case 2:
                res = dequeue(&item, queue);
                if (!res)
                    printf("\'%c\' has beed dequeued.\n", item);
                break;
        }

        print_queue(queue);
    }

    return 0;
}