检验C语言合法标识符的题目,为什么我的代码wrong answer?

Question

网址:http://acm.hdu.edu.cn/showproblem.php?pid=2024
#include <iostream>
#include <string>
using namespace std;

int main()
{
int n;
char ch[50];
int index;

char temp[20];
int i;
int flag;

string sys[32] = {"auto", "break", "case", "char", "const", "continue", "default",
"do", "double", "else", "enum", "extern", "float", "for", "goto",
"if", "int", "long", "register", "return", "short", "signed",
"sizeof", "static", "strUCt", "switch", "typedef", "union", "unsigned",
"void", "volatile", "while"};

cin>>n;
cin.get();
for(i=0; i<n; i++)
{

for(index=0; index<50; index++)
ch[index]=0;
cin.getline(ch,sizeof(ch));

for(index=0; index<32; index++)
{
strcpy(temp,sys[index].c_str());
if(strcmp(ch,temp)==0)
break;
}
if(index!=32)
{
cout<<"no"<<endl;
continue;
}

if(!((ch[0]=='_')||(ch[0]>='A' && ch[0]<='Z') || (ch[0]>='a' && ch[0]<='z')))
cout<<"no"<<endl;
else
for(index=49; index>0; index--)
{
if((ch[index]=='_')||(ch[index]>='A' && ch[index]<='Z') || (ch[index]>='a' && ch[index]<='z'))
{
flag=index;
break;
}
}//end for
for(index=1; index<=flag; index++)
{

if(ch[index]=='_'||(ch[index]>='A' && ch[index]<='Z') || (ch[index]>='a' && ch[index]<='z')
||(ch[index]>='0' && ch[index]<='9'))
continue;
cout<<"no"<<endl;
break;
}
}

return 0;
}

Answer 1

首先，buffer不够大。