队列创建和操作

//Author:Guo R.H
//Date:06.12.25
//   USTC

#include
#include

typedef struct QNode
{
 int data;
 struct QNode *next;
}QNode, *QPtr;
typedef struct QLink
{
 QPtr front;
 QPtr rear;
}QLink;

void Error(char *s)
{
 printf("%s\n",s);
}

void InitQueue(QLink *Q)
{
 Q->front = ( QPtr )malloc(sizeof(QNode));
 if(!Q->front)
 {
  Error("InitQueue memory error!");
  exit(0);
 }
 Q->rear = Q->front;
 Q->front->next = NULL;
}
void ClearQueue(QLink *Q)
{
 QPtr q, p = Q->front->next;
 Q->rear = Q->front;
 Q->front->next = NULL;
 while(p)
 {
  q = p;
  p = p->next;
  free(q);
 } 
}
void DestroyQueue(QLink *Q)
{
 while(Q->front)
 {
  Q->rear = Q->front->next;
  free(Q->front);
  Q->front = Q->rear;
 }
}
void EnQueue(QLink *Q, int i)
{
 QPtr p;
 p = ( QPtr )malloc(sizeof(QNode));
 if(!p)
 {
  Error("EnQueue memory error!");
  exit(0);
 }
 p->data = i;
 p->next = NULL;
 Q->rear->next = p;
 Q->rear = p;
}
void DeQueue(QLink *Q, int *i)
{
 QNode *p;
 if(Q->front == Q->rear)
 {
  Error("empty queue!");
  exit(0);
 }
 p = Q->front->next;
 *i = p->data;
 Q->front->next = p->next;
 if(p == Q->rear)
  Q->rear = Q->front;
 free(p);
}
void GetHead(QLink *Q, int *i)
{
 if(Q->front == Q->rear)
 {
  Error("empty queue!");
  exit(0);
 }
 *i = Q->front->next->data;
}
int EmptyQueue(QLink *Q)
{
 if(Q->front == Q->rear)
  return 1;
 else
  return 0;
}
int GetLength(QLink *Q)
{
 QPtr p=Q->front;
 int i=0;
 while(p != Q->rear)
 {
  i++;
  p = p->next;
 }
 return i;
}

int main()
{
 QLink Q;
 int i, t;
 InitQueue(&Q);
 for(i=0; i<5; i++)
  EnQueue(&Q, i+1);
 GetHead(&Q, &t);
 printf("%d\n", GetLength(&Q));
 ClearQueue(&Q);
 DeQueue(&Q, &t);
 printf("%d ", t);
 DestroyQueue(&Q);
 return 0;
}