Question

c语言循环队列的错误修改

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

#define maxqsize 10
#define overlow 0
#define error 0
#define ok 1

typedef struct {
char *base;
int front;
int rear;
} sqqueue;

int initqueue_sq(sqqueue *q) { //初始化顺序队
q->base = (char *) malloc(maxqsize * sizeof (char));
if (!q->base)
return overlow; //存储分配失败
q->front = q->rear = 0;
return ok;
}

int enqueue_sq(sqqueue *q, char e) { //e插入队尾作为新元素
if ((q->rear + 1) % maxqsize == q->front)
return error; //存储分配失败
q->base[q->rear] = e;
q->rear = (q->rear + 1) % maxqsize;
return ok;
}

int dequeue_sq(sqqueue *q, char *e) { //出队，返回首元素e的值
if (q->front == q->rear)
return error;
*e = q->base[q->front];
q->front = (q->front + 1) % maxqsize;
return ok;
}

int queuelength_sq(sqqueue *q) //求对长
{
return (q->rear - q->front + maxqsize) % maxqsize;
}

int queuetraverse_sq(sqqueue q, int(*visit)()) { //遍历顺序循环队
int i, n;
n = queuelength_sq(&q);
for (i = 0; i < n; i++)
visit(q.base + i);
return ok;
}

int visit(char (q.base)) {
printf("%c", *(q.base));
return ok;
}

int main() {
sqqueue q;
char e;
int i, n, m;
initqueue_sq(&q);
printf("input the number of the datas:");
scanf("%d", &n);
for (i = 0; i < n; i++) {
fflush(stdin);
printf("enter the queue:");
scanf("%c", &e);
if (!enqueue_sq(&q, e)) {
printf("the queue is full!\n");
break;
}
}
printf("traverse the queue now:");
queuetraverse_sq(q, int(*e));
printf("\nthe length of the queue is %d\n", queuelength_sq(&q));
printf("input the number of the datas to out:");
scanf("%d", &m);
for (i = 0; i < m; i++) {
printf("output the first data in the queue:");
dequeue_sq(&q, &e);
printf("%c\n", e);
}
printf("traverse the queue now:");
queuetraverse_sq(q, (*visit));
printf("\nthe length of the queue is %d\n", queuelength_sq(&q));
}
照高金山 - 首席运营官 十三级的方法改了一下：有新的错误，见：
http://zhidao.baidu.com/question/73368678.html
查资料后来是fflush(stdin)的用法问题：我的确和参考资料一样，用的是linux的gcc,fflush(stdin)这个函数在linux下没用，请朋友帮忙在linux下修改：
参考资料如下：
http://cpp.ga-la.com/html/3/3/0510/6.htm

Answer 1

彻底修改好了，请看：
#include <stdio.h>
#include <stdlib.h>
#include <malloc.h>

#define maxqsize 10
#define overlow 0
#define error 0
#define ok 1

typedef struct
{
char *base;
int front;
int rear;
} sqqueue;

int initqueue_sq(sqqueue *q)
{ //初始化顺序队
q->base = (char *) malloc(maxqsize * sizeof (char));
if (!q->base)
return overlow; //存储分配失败
q->front = q->rear = 0;
return ok;
}

int enqueue_sq(sqqueue *q, char e)
{ //e插入队尾作为新元素
if ((q->rear + 1) % maxqsize == q->front)
return error; //存储分配失败
q->base[q->rear] = e;
q->rear = (q->rear + 1) % maxqsize;
return ok;
}

int dequeue_sq(sqqueue *q, char *e)
{ //出队，返回首元素e的值
if (q->front == q->rear)
return error;
*e = q->base[q->front];
q->front = (q->front + 1) % maxqsize;
return ok;
}

int queuelength_sq(sqqueue *q) //求对长
{
return (q->rear - q->front + maxqsize) % maxqsize;
}

//int queuetraverse_sq(sqqueue q, int(*visit)()) //这里的参数visit应该跟下面的函数visit格式一致
int queuetraverse_sq(sqqueue q, int(*visit)(char *))
{ //遍历顺序循环队
int i, n;

n = queuelength_sq(&q);
for (i = 0; i < n; i++)
//visit(q.base + i); //应该从front遍历到rear，而不是从base开始，直接遍历N个元素
visit(q.base + (q.front+i)%maxqsize);
return ok;
}

//#-----------------这个函数写的问题有问题
/*int visit(char (q.base))
{
printf("%c", *(q.base));
return ok;
} */
//#---------------------------------
int visit(char *base)
{
printf("%c", *base);
return ok;
}

int main()
{
sqqueue q;
char e;
int i, n, m;

initqueue_sq(&q);
printf("input the number of the datas:");
scanf("%d", &n);
for (i = 0; i < n; i++)
{
//fflush(stdin);//用下面几句代码，替换fflush
int c;

if(feof(stdin) || ferror(stdin))
{
break;
}
while ( (c = getchar()) != '\n' && c != EOF ) ;

printf("enter the queue:");
scanf("%c", &e);
if(!enqueue_sq(&q, e))
{
printf("the queue is full!\n");
break;
}
}
printf("traverse the queue now:");
//queuetraverse_sq(q, int(*e));//不知道你这样写，有什么意图，应该是下面这句的吧？
queuetraverse_sq(q, (*visit));
printf("\nthe length of the queue is %d\n", queuelength_sq(&q));
printf("input the number of the datas to out:");
scanf("%d", &m);
for (i = 0; i < m; i++)
{
printf("output the first data in the queue:");
dequeue_sq(&q, &e);
printf("%c\n", e);
}
printf("traverse the queue now:");
queuetraverse_sq(q, (*visit));
printf("\nthe length of the queue is %d\n", queuelength_sq(&q));
getchar();getchar();//暂停一下
}

Answer 2

函数visit定义时形参char（q.base)不可用，改成一个指针char *a即可；

main函数里：第一个for循环结束后第二行：queuetraverse_sq(q, int(*e));
e不能做queuetraverse_sq（这个函数名太长了....我后面写函数1好吧）的实参。函数1的形参2是一个指向函数的指针。实际上函数1不需要第二个参数，在定义的时候直接写queuestraverse_sq(sqqueue q){/*....*/}就可以了。

最后把所有函数1的第二参数都删掉就行了。

Answer 3

1. 调用 queuetraverse_sq
queuetraverse_sq(q, int(*e));
-->>
queuetraverse_sq(q, (*visit));
2. 定义queuetraverse_sq
int queuetraverse_sq(sqqueue q, int(*visit)())
-->>
int queuetraverse_sq(sqqueue q, int(*visit)(char*))
3. 定义visit
int visit(char (q.base)) {
printf("%c", *(q.base));
return ok;
}
-->>
int visit(char* base) {
printf("%c", *base);
return ok;
}