#include "queue.h"

void initQueue(Queue q)
{
    q->qhead = NULL;
    q->qtail = NULL;
}

void enQueue(Queue q, int y)
{
    elem * tmp = (elem*)malloc(sizeof(elem));

    if (!tmp)
        retreat("fail to enQueue");
    tmp->y = y;
    tmp->next = NULL;

    if (!q->qtail)
    {
        q->qtail = tmp;
        q->qhead = tmp;
    }
    else
    {
        q->qtail->next = tmp;
        q->qtail = tmp;
    }
}

int deQueue(Queue q)
{
    bool flag = false;
    if (!q->qhead)
        retreat("Empty queue");
    if (q->qhead == q->qtail)
        flag = true;
    elem * tmp = q->qhead;
    int p = tmp->y;
    q->qhead = tmp->next;
    free(tmp);
    if (flag)
        q->qtail = q->qhead;
    return p;
}

bool emptyQueue(Queue q)
{
    if (q->qhead)
        return false;
    return true;
}

void purgeQueue(Queue q)
{
    elem * tmp;
    while (q->qhead)
    {
        tmp = q->qhead;
        q->qhead = tmp->next;
        free(tmp);
    }
}

void printHead(Queue q)
{
    printf("Queue head is %d\n", q->qhead->y);
}

void printQueue(Queue q)
{
    elem * tmp = q->qhead;
    while (tmp)
    {
        printf("%d  ",tmp->y);
        tmp = tmp->next;
    }
    printf("\n");
}