Question

输入一个字符串，判断其是否是C语言的合法标识符。

#include<stdio.h>
void main()
{
char ch[80],x;
int i=1;
scanf("%c",&x);
if(x=='_'||x>='a'&&x<='z'||x>='A'&&x<='Z')
while(i<80){
gets(ch);
if(ch[i]=='_'||ch[i]>='a'&&ch[i]<='z'||ch[i]>='A'&&ch[i]<='Z'||ch[i]>='0'&&ch[i]<='9') i++;
else
if (ch[i]=='\0') printf("yes");
else printf("no");
}
else printf("no");
}
代码哪里有问题？无法判断是标识符

Answer 1

#include<stdio.h>
void main()
{
char ch[800],x;
int i=0;
while(gets(ch))
{
i = 0;
//数字开头
if(ch[i]>= '0' && ch[i] <= 9)
{
printf("no");
continue
}
for(; ch[i] != '\0'; )
{
if(ch[i]=='_'||ch[i]>='a'&&ch[i]<='z'||ch[i]>='A'&&ch[i]<='Z'||ch[i]>='0'&&ch[i]<='9')
i++;
else
break;

}
if (ch[i]=='\0') printf("yes");
else printf("no");
}

Answer 2

#include<stdio.h>
int main()
{
char ch[80];
int i=0;
scanf("%s",ch);
if(ch[i]=='_'||(ch[i]>='a'&&ch[i]<='z')||(ch[i]>='A'&&ch[i]<='Z'))
{
i++;
while(i<80)
{

if(ch[i]=='_'||(ch[i]>='a'&&ch[i]<='z')||(ch[i]>='A'&&ch[i]<='Z')||(ch[i]>='0'&&ch[i]<='9')) i++;
else if (ch[i]=='\0')
{
printf("yes");break;
}
else
{
printf("no");break;
}

}
}
else printf("no");
return 0;
}

Answer 3

我也不知道，我就坐在你前面