为什么出现这个错误 ld returned 1 exit status 请大家帮帮忙
#include <iostream>#include <string>
#include <cctype>
#include <vector>
#include <cstring>
#include <stdexcept>
using namespace std;
char daxiao(string a1){
char c='N';
for(auto b1:a1)
if(isupper(b1)){
c='Y';
break;
}
return c;
}
int main(){
string a;
char b;
cout<<"shuru"<<endl;
cin>>a;
b=daxiao(a);
cout<<b<<endl;
return 0;
}
