队列的实现—由数组实现

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

#define N 6

typedef int datatype;

typedef struct
{
 datatype data[N];
 int front;   // points to the postion before the first element of queue
 int rear;   // points to the last element of queue
} sequeue;

sequeue *CreateEmptyQueue()
{
 sequeue *sq;

 sq = (sequeue *)malloc(sizeof(sequeue));
 sq->front = sq->rear = 0;

 return sq;
}

int EmptyQueue(sequeue *sq)
{
 return (sq->front == sq->rear);
}

int FullQueue(sequeue *sq)
{
 return (((sq->rear + 1) % N) == sq->front);
}

void ClearQueue(sequeue *sq)
{
 sq->front = sq->rear;
}

void EnQueue(sequeue *sq, datatype x)
{
 sq->rear = (sq->rear + 1) % N;
 sq->data[sq->rear] = x;

 return;
}

datatype DeQueue(sequeue *sq)
{
 sq->front = (sq->front + 1) % N;

 return sq->data[sq->front];
}