Red (queue)

/* NAPOMENA:
Program je napravljen samo na osnovu onoga sto sam procitao u skripti, ne mora znaciti da je tacan.
I nisam napisao sve funkcije, mrsko mi :)
*/

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

#define QUEUE_NULL -1

typedef int queueType;

typedef struct queueNodeStruct {
    struct queueNodeStruct *next;
    queueType data;
} queueNode;

void push(queueNode **top, queueType data) {
    queueNode *current;
    queueNode *next;
    queueNode *newNode;

    newNode = (queueNode *)malloc(sizeof(queueNode));
    newNode->data = data;
    newNode->next = NULL;

    if (*top == NULL) {
        *top = newNode;
        return;
    }

    current = next = *top;

    while (next->next != NULL) {
        current = next;
        next = current->next;
    }

    next->next = newNode;
}

queueType pop(queueNode **top) {
    queueType tmpData;
    queueNode *current;

    if (*top == NULL)
        return QUEUE_NULL;

    current = *top;
    tmpData = current->data;
    *top = current->next;
    free(current);

    return tmpData;
}

queueType front(queueNode **top) {
    queueNode *current;

    if (*top == NULL)
        return QUEUE_NULL;

    current = *top;

    return current->data;
}


int main() {
    queueNode *top;
    top = NULL;

    push(&top, 1);
    push(&top, 2);
    push(&top, 3);

    printf("%i", pop(&top));
    printf("%i", front(&top));
    printf("%i", pop(&top));
    printf("%i", pop(&top));


    return 0;
}