c++链表在执行完模块后跳出程序


#include
#include
#include
using namespace std;
struct student
{
    char name[20];
    char num[20];
    int math;
    int english;
    int py;
    int sum;
    int average;
};
struct node
{
    struct student data;
    struct node*next;
    
};
struct node*headnode;
struct node* createhead()
{  
    struct node*headnode=(struct node*)malloc(sizeof(struct node));
    assert(headnode);//判断是否申请内存成功
    headnode->next=NULL;
    return headnode;
    
}
struct node* createnode(struct student data)
{
    struct node*newnode=(struct node*)malloc(sizeof(struct node));
    assert(newnode);//判断是否申请内存成功
    newnode->data=data;
    newnode->next=NULL;
    return newnode;
    
}
void insertnode(struct node*headnode,struct student data)//headnote只需要，createnode函数只用调用一次 ，后面只需传入头节点就行 
{
 
    struct node*newnode=createnode(data);
    newnode->next=headnode->next;
    headnode->next=newnode;
   
    
}
void printlist(struct node*headnode)
{   
    struct node*passnode=headnode->next;
    cout<<"姓名"<<"\t" <<"编号"<<"\t" <<"数学"<<"\t" <<"英语"<<"\t"<<"py"<<"\t"<<"总分"<<"\t"<<"平均分"<<"\t";
    while(passnode!=NULL)
    {
        cout<data.name<data.num<data.math<data.english<data.py<data.sum<data.average<<"\t";
        passnode=passnode->next;
    }
}
void makemenu()
{
    cout<<"---------链式学生管理系统----------"<"1.录入功能"<"2.浏览功能"<"3.查找功能"<"4.修改功能"<"5.删除功能"<"6.退出系统"<"-----------------------------------"<void deletedata(struct node*headnode,const char*name)
{
    struct node*prenode=headnode;
    struct node*curnode=headnode->next;
    while(curnode!=NULL&&strcmp(curnode->data.name,name))
    {
        prenode=curnode;
        curnode=prenode->next;
    }
    if(curnode=NULL)
    {
        cout<<"删除失败，没有找到指定数据"<else
    {
        prenode->next=curnode->next;
        free(curnode);
    }
}
struct node*searchdata(struct node*headnode,const char*name)
{
    struct node*pmove=headnode->next;
    while(pmove!=NULL&&strcmp(pmove->data.name,name))
    {
        pmove=pmove->next;
    }
    return pmove;
}
void keydown()
{int m;
cin>>m;
struct student temp;
struct node*result;
    switch(m)
    {
        case 1:cout<<"----【录入模块】----"<"请输入学生信息："<"姓名"<<"\t" <<"编号"<<"\t" <<"数学"<<"\t" <<"英语"<<"\t"<<"py"<>temp.name>>temp.num>>temp.math>>temp.english>>temp.py;
         temp.sum=temp.math+temp.english+temp.py;
         temp.average=temp.sum/3;
         insertnode(headnode,temp);
        break;
        
        case 2:cout<<"----【浏览模块】----"<printlist(headnode);
        break;
        
        case 3:cout<<"----【查找功能】----"<"请输入要查找的名字：";
        cin>>temp.name;
        searchdata(headnode,temp.name);
        result=searchdata(headnode,temp.name);
        if(result==NULL)
        {
            cout<<"未找到结果"; 
        }
        else
        {
            cout<<"姓名"<<"\t" <<"编号"<<"\t" <<"数学"<<"\t" <<"英语"<<"\t"<<"py"<<"\t"<<"总分"<<"\t"<<"平均分"<<"\t";
                cout<data.name
                    <data.num
                    <data.math
                    <data.english
                    <data.py
                    <data.sum
                    <data.average<<"\t";
        }
        break; 
        
        case 4:cout<<"----【修改功能】----"<"请输入要修改的名字：";
        cin>>temp.name;
        searchdata(headnode,temp.name);
        result=searchdata(headnode,temp.name);
        if(result==NULL)
        {
            cout<<"未找到结果"; 
        }
        else
        {cout<<"输入新同学信息：" ; 
            cout<<"姓名"<<"\t" <<"编号"<<"\t" <<"数学"<<"\t" <<"英语"<<"\t"<<"py"<<"\t"<<"总分"<<"\t"<<"平均分"<<"\t";
            
            
        scanf("%s%s%d%d%d",result->data.name,20,result->data.num,20,&result->data.math,&result->data.english,&result->data.py);
                result->data.sum=result->data.math+result->data.english+result->data.py;
         result->data.average=result->data.sum/3;
        }
        break;
        
        case 5:cout<<"----【删除功能】----"<"请输入要删除的学生姓名：";
        cin>>temp.name ;
        deletedata(headnode,temp.name);
        break;
        
        case 6:cout<<"----【退出系统】----"<exit(0);
        break;    
        
        default:
               cout<<"输入错误，请重新输入！"<break;
    }
}


int main()
{ struct node*headnode=createhead();
    while(1)
    {
        makemenu();
        keydown();
        system("pause");
        system("cls");
    }
    return 0;
}

img

为啥这会直接退出程序啊，求解

输出显示程序崩溃了
178行， struct node*headnode=createhead();改为 headnode=createhead();
因为headnode已经是全局变量了，你这里又定义一个局部变量。导致实际全局变量headnode并没有初始化，所以其它函数使用headnode就会崩溃