一段程序中，cin为什么会解决这个问题，而scanf为什么会引起错误！

Question

这是我的这一段代码，当scanf时

#include<iostream>
#include<cstdio>
#include<cstdlib>
using namespace std;
typedef struct {    
char name[20];    
int wuwen;    
int shuxue;    
int yingyu;    
int number;
}student;
typedef struct listnode {    
student data;    
struct listnode* next;
}listnode, * linklist;
linklist l = NULL;
FILE* fp;
char filename[100];
void createlist() {    
l = (listnode*)malloc(sizeof(listnode));
l->next = NULL;}
void openfile() {    
createlist();    
listnode* p, * q;    
q = l;    
while (true) {        
printf("\n\n\t\t\t请输入文件名:");        

scanf("%s", &filename);        
if ((fp = fopen(filename, "r")) == NULL) {        
    printf("\t\t\t没有该文件,需要创建s\n");    
        char ch; scanf("%c",&ch);            
if (ch == 's') {                

if ((fp = fopen(filename, "a+")) == NULL) {                    
printf("\t\t\t创建文件失败\n");    
            }                
else break;            
}            
else continue;        
}        
else break;    
}    
while (true) {        
p = (listnode*)malloc(sizeof(listnode));    
if (fscanf(fp, "%d\t%s\t%d\t%d\t%d", &p->data.number, &p->data.name, &p->data.wuwen, &p->data.shuxue, &p->data.yingyu) == EOF) {            
free(p);            
printf("\t\t\t读入成功\n");            
system("pause");            
break;        
}        
p->next = NULL;        
q->next = p;        
q = q->next;    
}    
fclose(fp);
}
int main() {    
openfile();
}
当为cin时，就可以解决这个问题

#include<iostream>
#include<cstdio>
#include<cstdlib>
using namespace std;
typedef struct {    
char name[20];    
int wuwen;    
int shuxue;    
int yingyu;    
int number;
}student;
typedef struct listnode {    
student data;    
struct listnode* next;
}listnode, * linklist;
linklist l = NULL;
FILE* fp;
char filename[100];
void createlist() {    
l = (listnode*)malloc(sizeof(listnode));
l->next = NULL;}
void openfile() {    
createlist();    
listnode* p, * q;    
q = l;    
while (true) {        
printf("\n\n\t\t\t请输入文件名:");        

scanf("%s", &filename);        
if ((fp = fopen(filename, "r")) == NULL) {        
    printf("\t\t\t没有该文件,需要创建s\n");    
        char ch; cin >> ch;            
if (ch == 's') {                

if ((fp = fopen(filename, "a+")) == NULL) {                    
printf("\t\t\t创建文件失败\n");    
            }                
else break;            
}            
else continue;        
}        
else break;    
}    
while (true) {        
p = (listnode*)malloc(sizeof(listnode));    
if (fscanf(fp, "%d\t%s\t%d\t%d\t%d", &p->data.number, &p->data.name, &p->data.wuwen, &p->data.shuxue, &p->data.yingyu) == EOF) {            
free(p);            
printf("\t\t\t读入成功\n");            
system("pause");            
break;        
}        
p->next = NULL;        
q->next = p;        
q = q->next;    
}    
fclose(fp);
}
int main() {    
openfile();
}

所以，我就是想知道，为什么scanf会引起这样的错误

Answer 1

scanf如果输入字符，会接收换行符的