openjudge / 1.7编程基础之字符串 06

06:合法 C 标识符

#include<bits/stdc++.h>
using namespace std;  
const int N = 21;  
char S[N]; 
int main(){ gets(S); int n = strlen(S);bool flag = 1;if (!(S[0]=='_' || isalpha(S[0])))flag = 0;else{for (int i=1; i<n; i++)  {  if (!(S[i]=='_' || isalnum(S[i]))){flag = 0;break;}}  }if (flag)cout << "yes" << endl;elsecout << "no" << endl;return 0;     
}