//队列，队首删除，队尾插入, 先进先出
#include<stdio.h>
#define MaxSize 100
typedef char ElemType;
typedef struct
{
ElemType queue[MaxSize];
int front,rear;
}queue;
//init a queue
void initqueue(queue *Q)
{
Q->front=Q->rear=-1;
}
//Enter the queue
void enter(queue *Q,ElemType x)
{
if(Q->rear==MaxSize)
{
printf("The queue is too long~\n");
}
else
{
Q->rear++;//remove the rear
Q->queue[Q->rear]=x;
}
}
//Delete an element
void del(queue *Q)
{
if(Q->front==Q->rear)
{
printf("Empty  queue!\n");
}
else
Q->front++;
}
//Get the first element
ElemType gethead(queue *Q)
{
if(Q->front==Q->rear)
{
printf("Empty  queue!\n");
}
else
return(Q->queue[Q->front+1]);
}
//Empty or not
void empty(queue *Q)
{
if(Q->front==Q->rear)
{
printf("Empty  queue!\n");
}
else
{
printf("Not wmpty.");
}
}
//Display the queue
void display(queue *Q)
{
int i;
printf("The element in the queue:\n");
for(i=Q->front+1;i<=Q->rear;i++)
{
printf("%5c",Q->queue[i]);
}
printf("\n");
}
void main()
{
queue a;
queue *q=&a;
printf("Inital:\n");
initqueue(q);
printf("Empty?:\n");
empty(q);
printf("Enter some word:\n");
enter(q,'q');
enter(q,'w');
enter(q,'d');
enter(q,'a');
display(q);
printf("Delete one.:\n");
del(q);
display(q);
printf("The first Elem:%c\n",gethead(q));
printf("Hello!\n");
}