AC日记——合法C标识符 openjudge 1.7 06

#include<cstdio>
#include<string>
#include<iostream>
#include<algorithm>

using namespace std;

int len;

string word;

int main()
{
    cin>>word;
    len=word.length();
    if(word[0]<=‘9‘&&word[0]>=‘0‘)
    {
        printf("no\n");
        return 0;
    }
    for(int i=0;i<len;i++)
    {
        if((word[i]<‘0‘||word[i]>‘9‘)&&(word[i]>‘z‘||word[i]<‘a‘)&&(word[i]>‘Z‘||word[i]<‘A‘)&&word[i]!=‘_‘)
        {
            printf("no\n");
            return 0;
        }
    }
    printf("yes\n");
    return 0;
}