#define MAX_QUEUE 10000
typedef struct {
    int *stackA;
    int *stackB;
    int topA;
    int topB;
} CQueue;


CQueue* cQueueCreate() {
    CQueue *cq;
    cq = (CQueue*)malloc(sizeof(CQueue));
    if(cq == NULL)
    return NULL;
    cq->stackA = (int*)malloc(MAX_QUEUE * sizeof(int));
    if(cq->stackA == NULL)
    {
        free(cq);
    return NULL;
    }
    cq->topA = -1;
    cq->stackB = (int*)malloc(MAX_QUEUE * sizeof(int));
    if(cq->stackB == NULL)
    {
        free(cq->stackA);
        free(cq);
    return NULL;
    }
    cq->topB = -1;
    return cq;
}

void cQueueAppendTail(CQueue* obj, int value) {
    if(obj->topA != MAX_QUEUE)
    {
        obj->stackA[++obj->topA] = value;
    }
}

int cQueueDeleteHead(CQueue* obj) {
    int topBElem = 0;
    int topAElem = 0;

    if(obj->topB != -1)
    {
       topBElem = obj->stackB[obj->topB--];
       return topBElem;
    }
    
    if(obj->topB == -1 && obj->topA != -1)
    {
        while(obj->topA != -1)
        {
            topAElem = obj->stackA[obj->topA--];
            obj->stackB[++obj->topB] = topAElem;
        } 
    }

    if(obj->topB != -1)
    {
        topBElem = obj->stackB[obj->topB--];
        return topBElem;
    }
    return -1;
}

void cQueueFree(CQueue* obj) {
    if(obj != NULL)
    {
        if(obj->stackA != NULL)
        free(obj->stackA);
        if(obj->stackB != NULL)
        free(obj->stackB);
        free(obj);
    }
}