问题描述：停车场是一个能放n辆车的狭长通道，只有一个大门，汽车按到达的先后次序停放。若车场满了，车要停在门外的便道上等候，一旦有车走，则便道上第一辆车进入。当停车场中的车离开时，由于通道窄，在它后面呢的车要先退出，待它走后再依次进入。汽车离开时按停放时间收费。

基本功能要求：

（1）建立三个数据结构分别是：停放队列、让路栈、等候队列。
（2）输入数据模拟管理过程，数据（入或出，车号）。

停车管理系统是C语言中队列和栈比较简单的应用，需要注意的是停车队列、等候队列、让路栈结构体的构建。在写代码时，出队列入栈和出栈入队列时，指针容易出错而造成段错误，应当注意。我所写的代码如下：

//定义结构体

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

#define F 0
#define T 1
#define MAX 3

typedef struct Node  //数据
{
  int number;
  int time;
}Node;

typedef struct QueueNode  //队列结点
{
  struct Node infom;
  struct QueueNode * next;
}*QueueNode;

typedef struct LinkQueue  //链队列
{
  struct QueueNode * front;
  struct QueueNode * rear;
}LinkQueue;

typedef struct stack     //栈结点
{
  struct Node data;
  struct stack *next;
}*StackNode;

typedef struct LinkStack   //链栈
{
  StackNode top;
  int count;
}LinkStack;

//函数实现

void menu(LinkQueue *wait,LinkQueue *park,LinkStack *giveway,int num,int t);//菜单
int init(LinkQueue *wait,LinkQueue *park,LinkStack *giveway);//初始化
int linklength(LinkQueue q);//查看长度
int enqueue(LinkQueue *q,int num,int t);//入队列
int dequeue(LinkQueue *q,int *num,int *t);//出队列
void park1(LinkQueue *wait,LinkQueue *park);//停车函数
int push(LinkStack *s,int num,int t);//入栈
int pop(LinkStack *s,int *num,int *t);//出栈
void leave2(LinkQueue *wait,LinkQueue *park,LinkStack *giveway,int num,int t);//离开函数
void view3(LinkQueue wait,LinkQueue park);//查看停车场状态

int main()
{
  LinkQueue wait;
  LinkQueue park;
  LinkStack giveway;
  int num = 0;
  int t = 0;
  init(&wait,&park,&giveway);
  menu(&wait,&park,&giveway,num,t);
  return 0;
}

int init(LinkQueue *wait,LinkQueue *park,LinkStack *giveway)
{
  QueueNode newnode1 = (QueueNode)malloc(sizeof(struct QueueNode));
  if(NULL == newnode1)
  {
    return F;
  }
  newnode1->next = NULL;
  wait->front = newnode1;
  wait->rear = newnode1;

  QueueNode newnode2 = (QueueNode)malloc(sizeof(struct QueueNode));
  if(NULL == newnode2)
  {
    return F;
  }
  newnode2->next = NULL;
  park->front = newnode2;
  park->rear = newnode2;

  giveway->top = NULL;
  giveway->count = 0;
}

void menu(LinkQueue *wait,LinkQueue *park,LinkStack *giveway,int num,int t)
{
  printf("**********Welcome to our Car Parking !**********\n");
  printf("********** Please choose function  **********\n");
  printf("**********     1 : park.     **********\n");
  printf("**********     2 : leave.     **********\n");
  printf("**********     3 : view.     **********\n");
  printf("**********     4 : exit.     **********\n");
  int option;
  scanf("%d",&option);
  switch(option)
  {
    case 1:{
      park1(wait,park);
      printf("停车完成！\n");
      menu(wait,park,giveway,num,t);
      break;
    }
    case 2:{
      leave2(wait,park,giveway,num,t);
      menu(wait,park,giveway,num,t);
      break;
    }
    case 3:{
      view3(*wait,*park);
      menu(wait,park,giveway,num,t);
      break;
    }
    case 4:{
      printf("**********   欢迎再次使用，谢谢！  **********\n");
      break;
    }
    default:{
      printf("**********   请输入正确的指令！  **********\n");
      menu(wait,park,giveway,num,t);
      break;
    }
  }

}

int linklength(LinkQueue q)
{
  int i = 0;
  while(q.front != q.rear)
  {
    i++;
    q.front = q.front->next;
  }
  return i;
}

int enqueue(LinkQueue *q,int num,int t)
{
  QueueNode newnode = (QueueNode)malloc(sizeof(struct QueueNode));
  if(NULL == newnode)
  {
    return F;
  }
  newnode->infom.number = num;
  newnode->infom.time = t;
  newnode->next = NULL;
  q->rear->next = newnode;
  q->rear = newnode;
  return T;
}

int dequeue(LinkQueue *q,int *num,int *t)
{
  if(q->front == q->rear)
  {
    printf("the queue is empty!\n");
    return F;
  }
  *num = q->front->next->infom.number;
  *t = q->front->next->infom.time;
  QueueNode temp = q->front->next;
  q->front->next = temp->next;
  if(temp->next == NULL)
  {
    q->rear = q->front;
  }
  free(temp);
  return T;
}

void park1(LinkQueue *wait,LinkQueue *park)
{
  printf("请输入车号和停车时间\n");
  int num,t;
  scanf("%d,%d",&num,&t);
  if(linklength(*park) >= MAX)
  {
    printf("停车场已满，进入等待区！\n");
    enqueue(wait,num,t);
  }
  else
  {
    enqueue(park,num,t);
  }
}

int push(LinkStack *s,int num,int t)
{
  StackNode newnode = (StackNode)malloc(sizeof(struct stack));
  if(NULL == newnode)
  {
    return F;
  }
  newnode->data.number = num;
  newnode->data.time = t;
  newnode->next = s->top;
  s->top = newnode;
  s->count++;
  return T;
}

int pop(LinkStack *s,int *num,int *t)
{
  if(0 == s->count)
  {
    printf("the stack is empty !\n");
    return F;
  }
  *num = s->top->data.number;
  *t = s->top->data.time;
  StackNode temp = s->top;
  s->top = s->top->next;
  free(temp);
  s->count--;
  return T;
}

void leave2(LinkQueue *wait,LinkQueue *park,LinkStack *giveway,int num,int t)
{
  printf("请输入要离开车的车号\n");
  int leavenumber;
  scanf("%d",&leavenumber);
  int i = 0;
  QueueNode head = park->front;
  while(head != park->rear)
  {
    if(head->next->infom.number != leavenumber)
    {
      head = head->next;
      i++;
    }
    else
      break;
  }
  int j = 0;
  if(i <= MAX-1)
  {
    while(j != i)
    {
      dequeue(park,&num,&t);
      push(giveway,num,t);
      j++;
    }
    dequeue(park,&num,&t);
  }
  else
  {
    printf("查无此车！\n");
  }
  while(giveway->top != NULL)
  {
    pop(giveway,&num,&t);
    enqueue(park,num,t);
  }
  if(linklength(*wait) != 0)
  {
    dequeue(wait,&num,&t);
    enqueue(park,num,t);
  }
}

void view3(LinkQueue wait,LinkQueue park)
{
  printf("********************  目前停车场状况  ********************\n");
  printf("停车场共%d个车位，当前停车场共有%d量车，等待区共有%d量车\n",
    MAX,linklength(park),linklength(wait));
  printf("**************************************************************\n");
  printf("车  号：");
  QueueNode head1 = park.front;
  QueueNode head2 = park.front;
  while(head1 != park.rear)
  {
    printf("%d ",head1->next->infom.number);
    head1 = head1->next;
  }
  printf("\n");
  printf("停车时间：");
  while(head2 != park.rear)
  {
    printf("%d ",head2->next->infom.time);
    head2 = head2->next;
  }
  printf("\n");
}