为什么程序会显示 head和p未定义
代码：
#include
#include
#include
#define MAX_STUDENTS 100
int s1;
typedef struct stu
{
char stuhao[20];
char stuname[20];
char sturiqi[4];
int score[6];
float pin;
int stuzong;
double sum;
double ave;
struct stu *next;
}stu;
stu student[100];
void daoru(stu *head,stu *p);
void shuchu(stu *head,stu *p);
void shuru(stu *head,stu *p);
void baocun(stu *head,stu *p);
void shanchu(stu *head,stu *p);
void paixu(stu *head,stu *p);
void tongji(stu *head,stu *p);
void menu2(stu *head,stu *p);
void xh(stu *head,stu *p);
void name(stu *head,stu *p);
void xuan1(stu *head,stu *p);
void xuan2(stu *head,stu *p);
void xuan3(stu *head,stu *p);
void xuan4(stu *head,stu *p);
void xuan5(stu *head,stu *p);
void xuan6(stu *head,stu *p);
void xueke(stu *head,stu *p);
void chaxun(stu *head,stu *p);
void denglu();
void xuanze(stu *head,stu *p);
void meun();
int main()
{
int i;
stu *temp=(stu *)malloc(sizeof(stu));
strcpy(temp->stuhao,"\0");
strcpy(temp->stuname,"\0");
strcpy(temp->sturiqi,"\0");
temp->score[1]=0;
temp->score[2]=0;
temp->score[3]=0;
temp->score[4]=0;
temp->score[5]=0;
temp->score[6]=0;
temp->sum=0;
temp->ave=0;
temp->next=NULL;
stu *head=temp;
stu *a=(stu *)malloc(sizeof(stu));
strcpy(a->stuhao,"\0");
strcpy(a->stuname,"\0");
strcpy(a->sturiqi,"\0");
a->score[1]=0;
a->score[2]=0;
a->score[3]=0;
a->score[4]=0;
a->score[5]=0;
a->score[6]=0;
a->sum=0;
a->ave=0;
a->next=NULL;
temp->next=a;
temp=temp->next;
stu *p=head;
int x=0,flag=1;
denglu();
if(x) flag=0;//判断是否进入界面
if(flag)
{
meun();
}
}
void daoru()
{
FILE *fp;
int i=1;
fp=fopen("数据.txt","r");
if(!fp)
{
printf("打开文件失败\n");
return;
}
i=0;
while(!feof(fp))
{
fscanf(fp,"%s %s %d %d &d &d &d &d &d &d\n",student[i].stuhao,student[i].stuname,
student[i].sturiqi[1],student[i].sturiqi[2],student[i].sturiqi[3],
student[i].score[1],student[i].score[2],student[i].score[3],student[i].score[4],student[i].score[5],student[i].score[6]);
i++;
}
fclose(fp);
s1=i-1;
}
void shuchu()
{
int i;
printf("学号\t 姓名 出生年月 成绩1 成绩2 成绩3 成绩4 成绩5 成绩6\n");
for(i=1;i<=s1;i++)
{
printf("%s %s %d年%d月%d日 %d %d %d %d %d %d\n",student[i].stuhao,student[i].stuname,
student[i].sturiqi[1],student[i].sturiqi[2],student[i].sturiqi[3],
student[i].score[1],student[i].score[2],student[i].score[3],student[i].score[4],student[i].score[5],student[i].score[6]);
}
}
void shuru()
{
int i,j,flag=1,n,t=0,x=1;
stu *d=p,*h=head;
printf("请输入本次输入的学生数量\n");
scanf("%d",&n);
if(p==head) {p=p->next;n=n-2;t=1;}
for(i=1;i<=n;i++)
{
stu *a=(stu *)malloc(sizeof(stu));
strcpy(a->stuhao,"\0");
strcpy(a->stuname,"\0");
strcpy(a->sturiqi,"\0");
a->score[1]=0;
a->score[2]=0;
a->score[3]=0;
a->score[4]=0;
a->score[5]=0;
a->score[6]=0;
a->sum=0;
a->ave=0;
a->next=NULL;
p->next=a;
p=p->next;
}
p=d->next;//回到最初位置
if(t) {n+=2;p=head;}
for(i=1;i<=n;i++)
{
x=1;
while(x)
{
fflush(stdin);
printf("请输入学生学号\n");
gets(p->stuhao);
for(head=h;head!=p;head=head->next)
{
if(strcmp(head->stuhao,p->stuhao)==0){printf("学号重复！！！\n");break;}
}
if(head==p)x=0;
}
printf("请输入学生姓名\n");
gets(p->stuname);
printf("请输入学生生日\n");
gets(p->sturiqi);
fflush(stdin);
printf("请输入学生科目一成绩\n");
scanf("%lf",&p->score[1]);
printf("请输入学生科目二成绩\n");
scanf("%lf",&p->score[2]);
printf("请输入学生科目三成绩\n");
scanf("%lf",&p->score[3]);
printf("请输入学生科目四成绩\n");
scanf("%lf",&p->score[4]);
printf("请输入学生科目五成绩\n");
scanf("%lf",&p->score[5]);
printf("请输入学生科目六成绩\n");
scanf("%lf",&p->score[6]);
p->sum=p->score[1]+p->score[2]+p->score[3]+p->score[4]+p->score[5]+p->score[6];
p->ave=p->sum/6;
if(i!=n)p=p->next;//p最后指向链表最末节点的头上
}
return p;
}
void baocun()
{
for(;head!=(p->next);head=head->next)
{
printf(" 学号 姓名 生日 科目一成绩 科目二成绩 科目三成绩 科目四成绩 科目五成绩 科目六成绩 总成绩 平均成绩\n");
printf("%10s %5s %10s %6.2lf %6.2lf %6.2lf %6.2lf %6.2lf %6.2lf %6.2lf %6.2lf\n",head->stuhao,head->stuname,head->sturiqi,head->score[1],head->score[2],head->score[3],head->score[4],head->score[5],head->score[6],head->sum,head->ave);
}
}
void shanchu()
{
char a[20];
printf("请输入要删除的学生学号：");
scanf("%s",&a);
for(int i=1;i<=s1;i++)
{
if(strcmp(student[i].stuhao,a)==0)
{
break;
}
}
for(int i=1;i<=1;i++)
{
student[i]=student[i+1];
}
s1--;
printf("已经删除成功！\n");
}
void paixu()
{
stu *hd=head,*t=head,*ed=p,*td=NULL;
int i=0,chance=0;
char tnum[20],tname[20],tbirth[20];
double tscore1,tscore2,tscore3,tscore4,tscore5,tscore6,tsum,tave;
printf("请选择排序方式\n");
printf("（1）学号（2）年龄（3）总分\n");
scanf("%d",&chance);
switch(chance)
{
case 1:
for(t=head;t!=p;t=t->next)
{
for(head=hd;head!=p;head=head->next)
{
td=head->next;
if(strcmp(head->stuhao,td->stuhao)>0)
{
strcpy(tnum,td->stuhao);
strcpy(td->stuhao,head->stuhao);
strcpy(head->stuhao,tnum);
strcpy(tname,td->stuname);
strcpy(td->stuname,head->stuname);
strcpy(head->stuname,tname);
strcpy(tbirth,td->sturiqi);
strcpy(td->sturiqi,head->sturiqi);
strcpy(head->sturiqi,tbirth);
tscore1=td->score[1];
td->score[1]=head->score[1];
head->score[1]=tscore1;
tscore2=td->score[2];
td->score[2]=head->score[2];
head->score[2]=tscore2;
tscore3=td->score[3];
td->score[3]=head->score[3];
head->score[3]=tscore3;
tscore4=td->score[4];
td->score[4]=head->score[4];
head->score[4]=tscore4;
tscore5=td->score[5];
td->score[5]=head->score[5];
head->score[5]=tscore5;
tscore6=td->score[6];
td->score[6]=head->score[6];
head->score[6]=tscore6;
tsum=td->sum;
td->sum=head->sum;
head->sum=tsum;
tave=td->ave;
td->ave=head->ave;
head->ave=tave;
}
}
}break;
case 2:
for(t=head;t!=p;t=t->next)
{
for(head=hd;head!=p;head=head->next)
{
td=head->next;
if(strcmp(head->sturiqi,td->sturiqi)>0)
{
strcpy(tnum,td->stuhao);
strcpy(td->stuhao,head->stuhao);
strcpy(head->stuhao,tnum);
strcpy(tname,td->stuname);
strcpy(td->stuname,head->stuname);
strcpy(head->stuname,tname);
strcpy(tbirth,td->sturiqi);
strcpy(td->sturiqi,head->sturiqi);
strcpy(head->sturiqi,tbirth);
tscore1=td->score[1];
td->score[1]=head->score[1];
head->score[1]=tscore1;
tscore2=td->score[2];
td->score[2]=head->score[2];
head->score[2]=tscore2;
tscore3=td->score[3];
td->score[3]=head->score[3];
head->score[3]=tscore3;
tscore4=td->score[4];
td->score[4]=head->score[4];
head->score[4]=tscore4;
tscore5=td->score[5];
td->score[5]=head->score[5];
head->score[5]=tscore5;
tscore6=td->score[6];
td->score[6]=head->score[6];
head->score[6]=tscore6;
tsum=td->sum;
td->sum=head->sum;
head->sum=tsum;
tave=td->ave;
td->ave=head->ave;
head->ave=tave;
}
}
}break;
case 3:
for(t=head;t!=p;t=t->next)
{
for(head=hd;head!=p;head=head->next)
{
td=head->next;
if(head->sumif(student[i].score[1]<60)
{
printf("%s %s %d %d &d &d &d &d &d &d\n",student[i].stuhao,student[i].stuname,
student[i].sturiqi[1],student[i].sturiqi[2],student[i].sturiqi[3],
student[i].score[1],student[i].score[2],student[i].score[3],student[i].score[4],student[i].score[5],student[i].score[6]);
}
}
}
void xuan2()
{
int i;
printf("科目2不及格的名单：\n");
for(i=1;iif(student[i].score[2]<60)
{
printf("%s %s %d %d &d &d &d &d &d &d\n",student[i].stuhao,student[i].stuname,
student[i].sturiqi[1],student[i].sturiqi[2],student[i].sturiqi[3],
student[i].score[1],student[i].score[2],student[i].score[3],student[i].score[4],student[i].score[5],student[i].score[6]);
}
}
}
void xuan3()
{
int i;
printf("科目3不及格的名单：\n");
for(i=1;iif(student[i].score[3]<60)
{
printf("%s %s %d %d &d &d &d &d &d &d\n",student[i].stuhao,student[i].stuname,
student[i].sturiqi[1],student[i].sturiqi[2],student[i].sturiqi[3],
student[i].score[1],student[i].score[2],student[i].score[3],student[i].score[4],student[i].score[5],student[i].score[6]);
}
}
}void xuan4()
{
int i;
printf("科目4不及格的名单：\n");
for(i=1;iif(student[i].score[4]<60)
{
printf("%s %s %d %d &d &d &d &d &d &d\n",student[i].stuhao,student[i].stuname,
student[i].sturiqi[1],student[i].sturiqi[2],student[i].sturiqi[3],
student[i].score[1],student[i].score[2],student[i].score[3],student[i].score[4],student[i].score[5],student[i].score[6]);
}
}
}
void xuan5()
{
int i;
printf("科目5不及格的名单：\n");
for(i=1;iif(student[i].score[5]<60)
{
printf("%s %s %d %d &d &d &d &d &d &d\n",student[i].stuhao,student[i].stuname,
student[i].sturiqi[1],student[i].sturiqi[2],student[i].sturiqi[3],
student[i].score[1],student[i].score[2],student[i].score[3],student[i].score[4],student[i].score[5],student[i].score[6]);
}
}
}
void xuan6()
{
int i;
printf("科目6不及格的名单：\n");
for(i=1;iif(student[i].score[6]<60)
{
printf("%s %s %d %d &d &d &d &d &d &d\n",student[i].stuhao,student[i].stuname,
student[i].sturiqi[1],student[i].sturiqi[2],student[i].sturiqi[3],
student[i].score[1],student[i].score[2],student[i].score[3],student[i].score[4],student[i].score[5],student[i].score[6]);
}
}
}
void xueke()
{
int a;
printf("选择查询不及格的科目：");
scanf("%d,&a");
switch(a)
{
case 1:
xuan1();
break;
case 2:
xuan2();
break;
case 3:
xuan3();
break;
case 4:
xuan4();
break;
case 5:
xuan5();
break;
case 6:
xuan6();
break;
}
}
void chaxun()
{
int a;
menu2();
printf("请选择查询方式：");
scanf("%d",&a);
switch(a)
{
case 1:
xh();
break;
case 2:
name();
break;
case 3:
xueke();
break;
}
}
void denglu()
{
int i,flag=0;
char a[10],b[10],c[10],d[10];
FILE *fp;
printf("---------------登录-----------------\n");
for(i=1;i<=3;i++)
{
printf("请输入您的姓名：");
gets(a);
printf("请输入您的密码：");
gets(b);
fp=fopen("账号信息.txt","r");
if(fp==NULL)
{
perror("can not open file!");
exit(1);
}
while(fgets(c,sizeof(c),fp)) //逐行循环读取文件，直到文件结束或找到相同姓名
{
if(strstr(c,a))
{
fscanf(fp,"%s",d);
break;
}
}
if(strcmp(b,d)==0)
{
printf("---------------登录成功，进入系统----------\n");
flag=1;
break;
}
else printf("-------登录失败，请重新输入,您还有%d次机会--------\n",3-i);
fclose(fp);
}
if(flag==0)
exit(0);
}
void xuanze()
{
int a,b=3;
printf("请输入模式：");
scanf("%d",&a);
switch(a)
{
case 1:
shuru();
break;
case 2:
tongji();
break;
case 3:
shuchu();
break;
case 4:
chaxun();
break;
case 5:
paixu();
break;
case 6:
shanchu();
break;
case 7:
baocun();
break;
}
}
void meun()
{
printf("************************************************************\n");
printf("** 欢迎进入学生信息管理系统 **\n");
printf("** 1.信息录入 **\n");
printf("** 2.信息统计 **\n");
printf("** 3.信息浏览 **\n");
printf("** 4.信息查询 **\n");
printf("** 5.信息排序 **\n");
printf("** 6.信息删除 **\n");
printf("** 7.信息保存 **\n");
printf("************************************************************\n");
}
指出你的两个问题。
1.你的函数比如baocun，paixu声明和最后的定义逻辑实现部分的入参不一样，声明有参数，但实现的时候却没参数，虽然你调用的时候没有穿参数没有问题，但是这不是一个良好的编程习惯
2.报错和我刚才说的1有关，因为你的baocun，paixu等函数内部直接使用了head，但head并不是一个全局变量或者函数内定义的局部变量（包含栈空间内的入参），因此就会报错
如何解决呢，保持你的函数声明和定义的类型一样，也就是给你的baocun，paixu等函数实现部分加入像声明一样的参数
因为 head 跟 p 是函数 main 中的局部变量，在其它函数中是不可见的，所以会报错未定义，可以把 head 跟 p 放在 main 函数的外面定义就好了
head 和 p是定义在main函数里的，为局部变量，被封装在main函数里，对其他函数”不可见“。要想在其他函数里也使用head和p的定义，可以将head和p定义成全局变量
以上两位说的对，如果不在同一个.c使用，还需要加上extern呦。
不知道你这个问题是否已经解决, 如果还没有解决的话:Linknode* split(Linknode* head) {
Linknode *pre, *p;
pre = head;
p = head->next;
while (p->info % 2 != 0)
{
pre = p;
p = p->next;
}
while (p)
{
if (p->info % 2 == 1)
{
pre->next = p->next;
p->next = head->next;
head->next = p;
p = pre;
}
else
{
pre = p;
p=p->next;
}
}
return head;
}