队列的出队/入队的操作_题重新定义队列出队的操作:队首出队的数字重新在队尾入队。 例:队列中有1 2 3三个

#include <malloc.h>
#include <stdio.h>

typedef struct Node
{
    int data;
    struct Node *pNext;
}Node;

typedef struct Queue
{
    Node *first;
    Node *rear;
}Queue;

Queue *PushBack(Queue *Q,int num)
{
    Node *p = (Node *)malloc(sizeof(Node));
    p->data = num;
    p->pNext = NULL;

    if (Q->rear == NULL)//empty queue
    {
        Q->first = p;
        Q->rear = p;
    }
    else
    {
        Q->rear->pNext = p;
        Q->rear = p;
    }
    return Q;
}

int PopFirst(Queue *Q)
{
    int num;
    if (Q->first == NULL)
    {
        printf("Empty queue\n");
        return 0;
    }
    num = Q->first->data;
    Node *p;
    p = Q->first;
    if (Q->first == Q->rear)
    {
        Q->first = NULL;
        Q->rear = NULL;
    }
    else
    {
        Q->first = Q->first->pNext;
    }
    free(p);

    return num;
}

void test()
{
    Queue *Q;
    Q = (Queue *)malloc(sizeof(Queue));
    Q->first = NULL;
    Q->rear = NULL;
    PushBack(Q,1);
    PushBack(Q,2);
    PushBack(Q,3);
    PushBack(Q,4);
    PushBack(Q,5);

    printf("%d\n",PopFirst(Q));
    printf("%d\n",PopFirst(Q));
    printf("%d\n",PopFirst(Q));
    printf("%d\n",PopFirst(Q));
    printf("%d\n",PopFirst(Q));

    printf("%d\n",PopFirst(Q));

}
int main()
{

    test();
    return 0;
}


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output：
1
2
3
4
5
Empty queue
0