Aeiou

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

#ifndef DEBUG
#define DEBUG(...) printf(__VA_ARGS__)
#endif

#define SIZE 8

struct queue_s {
    int *array;
    int head;
    int tail;
} queue_init = { .head=0, .tail=0 };
typedef struct queue_s queue_t;


int enqueue(queue_t *queue, int val) {
    if ((queue->tail + 1) % SIZE == queue->head) return -1;

    queue->array[queue->tail] = val;
    queue->tail = (queue->tail + 1) % SIZE;

    return 0;
}

int dequeue(queue_t *queue) {
    if (queue->head == queue->tail) return -1;

    queue->head = (queue->head + 1) % SIZE;

    return 0;
}

int print(queue_t queue) {
    int i;

    if (queue.tail==queue.head) return -1;

    for (i=queue.head; i!=queue.tail; i=(i+1)%SIZE) {
        printf("%d ", queue.array[i]);
    }
    printf("\n");
    return 0;
}


int main() {
    int val, ret_val, menu_choice;
    char c;
    queue_t queue = queue_init;

    queue.array = (int *)malloc(sizeof(int)*SIZE);
    setbuf(stdout, NULL);
    do {
        menu_choice = 0;
        DEBUG("\n1 enqueue\n2 dequeue\n3 ispis (print)\n4 izlaz\n");
        scanf("%d", &menu_choice);
        switch (menu_choice) {
            case 1:
                scanf("%d", &val);
                ret_val = enqueue(&queue, val);
                if(ret_val==-1) printf("Red je pun.\n");
                break;
            case 2:
                ret_val = dequeue(&queue);
                if(ret_val==-1) printf("Red je prazan.\n");
                break;
            case 3:
                ret_val = print(queue);
                if(ret_val==-1) printf("Red je prazan.\n");
                break;
            case 4:
                break;
            default:
                while((c = getchar()) != '\n' && c != EOF);
        }
    } while(menu_choice!=4);
    free(queue.array);
    return 0;
}