循环队列—数组实现

/* circular queue: 牺牲一个存储节点，对头front指示的节点不用于存储数据，起标志性作用
* front: 队头元素的前一个位置
* rear： 队尾元素
*/
#include<stdio.h>
#include<stdlib.h>

#define MAX		10 //size of queue

int insertCircularQueue(int queue[], int front,int *rear, int value);
int delCircularQueue(int queue[], int *front, int rear, int  *value);
void printQueue(int queue[], int front, int rear);
void item();

int queue[MAX];
int front =0;//与初始值无关 0也也可以
int rear = 0;

main(void)
{
char item_choice;
int n;
item();
while(1)
{
item_choice = getchar();
switch (item_choice)
{
case '1':
printf("Insert a element to the queue: ");
scanf("%d", &n);
insertCircularQueue(queue, front,&rear, n);
printf("\nQueue: ");
printQueue(queue, front, rear);
putchar('\n');
item();
break;
case '2':
printf("Get an element from the queue: ");
delCircularQueue(queue, &front, rear, &n);
printf("Element: %d\n", n);
printf("Queue: ");
printQueue(queue, front, rear);
putchar('\n');
item();
break;
case '0':
printf("Good luck to you!\n");
return 0;
}
}
return;
}

/* insert a element into the end of queue */
/* 插入队尾，只有队尾值会改变，所以队尾要传入指针，而队头只需传入值即可 */
int insertCircularQueue(int queue[], int front, int *rear, int value)
{

*rear = (*rear + 1)%MAX;
if(*rear == front) {
printf("Queue overflow\n");
exit(-1);
}
queue[*rear] = value;
return 0;
}

/* delete an element at the head of queue */
/* 删除在对头，只有队头值会改变，所以队头要传入指针，而队尾只需传入值即可 */
int delCircularQueue(int queue[], int *front, int rear, int  *value)
{
if(*front == rear) {
printf("Queue underflow\n");
exit(-1);
}
*front = (*front+1)%MAX;
*value = queue[*front];
return 0;
}

/* print content of the queue, we use {} to contaion queue elements*/
void printQueue(int queue[], int front, int rear)
{
int i;
if(front == -1)
printf("{");
for(i=0; i<MAX; i++) {
printf("%d ", queue[i]);
if(i == front)
printf("{ ");

if(i == rear)
printf("} ");
}
putchar('\n');
}

void item()
{
printf("*************** Welcome to the Queue *************\n");
printf("1: Insert one element;\n");
printf("2: Delete one element;\n");
printf("0: Exit.\n");
printf("*************************************************\n");
printf("Select your operation: ");
}