队列实例程序（C语言）

/* queue.h */

#ifndef _QUEUE_H
#define _QUEUE_H

struct queue_record;
typedef struct queue_record *queue;

int is_empty( queue q );
int is_full( queue q );
queue create_queue( int max_elements );
void dispose_queue( queue q );
void make_empty( queue q );
void enqueue( int x, queue q );
int front( queue q );
void dequeue( queue q );
int front_and_dequeue( queue q );

#endif

/* queue.c */

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

#define MIN_QUEUE_SIZE    5

struct queue_record
{
int capacity;
int front;
int rear;
int size;
int *array;
};

void
make_empty( queue q )
{
q->size = 0;
q->front = 1;
q->rear = 0;
}

int
is_empty( queue q )
{
return q->size == 0;
}

int
is_full( queue q )
{
return q->size == q->capacity;
}

queue
create_queue( int max_elements )
{
queue q;

if( max_elements < MIN_QUEUE_SIZE )
{
printf("Queue size is too small!\n");
exit(0);
}

q = malloc( sizeof(struct queue_record) );
if(q == NULL)
{
printf("Out of space!\n");
exit(1);
}
q->array = malloc(sizeof(int) * max_elements);
if(q->array == NULL)
{
printf("Out of space!\n");
exit(1);
}
q->capacity = max_elements;

make_empty(q);

return q;
}

static int
succ( int value, queue q )
{
if( ++value == q->capacity )
value = 0;
return value;
}

void
enqueue( int x, queue q )
{
if( is_full( q ) )
{
printf("full queue!\n");
exit(0);
}
else
{
q->size++;
q->rear = succ( q->rear, q );
q->array[q->rear] = x;
}
}

void
dequeue( queue q )
{
if( is_empty( q ) )
{
printf("empty queue!\n");
exit(0);
}
else
{
q->size--;
q->front = succ( q->front, q );
}
}

int
front( queue q )
{

if( is_empty( q ) )
{
printf("empty queue!\n");
exit(0);
}
else
return q->array[q->front];
}

int
front_and_dequeue( queue q )
{
int tmp;

if( is_empty( q ) )
{
printf("empty queue!\n");
exit(0);
}
else
{
tmp = q->array[q->front];
q->size--;
q->front = succ( q->front, q );
return tmp;
}

}

void
dispose_queue( queue q )
{
if( q != NULL )
{
free(q->array);
free(q);
}
}

/* queue_test.c */

#include "queue.h"
#include <stdio.h>

int
main(void)
{
queue q;
int tmp;
int i;

q = create_queue(10);
printf("1 enqueue\n");
enqueue(1, q);
printf("2 enqueue\n");
enqueue(2, q);
printf("3 enqueue\n");
enqueue(3, q);
printf("4 enqueue\n");
enqueue(4, q);
printf("5 enqueue\n");
enqueue(5, q);

printf("\n");
for(i=0; i<5; i++)
{
printf("dequeue %d\n", front_and_dequeue( q ));

}

}