chaper3_exerise_Uva1568_Molar_Mass_分子量

 #include<iostream>
 #include<iomanip>
 #include<string>
 #include<cctype>
 using namespace std;
 const int maxn = ;

 void get_num(int &num,string c,int j)
 {
     while (isdigit(c[j]) && c[j])
     {
         num = num* + (c[j]-'');
         j++;
     }
 }

 int main(void)
 {
     string c;
     int T;
     cin >> T;
     for (int i = ; i < T; i++)
      {
          double count = ;
          cin >> c;
         for (int j = ; j < c.size(); j++)
         {
             if (isalpha(c[j]))
             {
                 if (isdigit(c[j+]))
                 {
                     int num = ;
                     get_num(num,c,j+);
                     switch(c[j])
                     {
                         case 'C' : count += 12.01*num; break;
                         case 'H' : count += 1.008*num; break;
                         case 'O' : count += 16.00*num; break;
                         case 'N' : count += 14.01*num; break;
                     }
                 }
                 else {
                         switch(c[j])
                         {
                             case 'C' : count += 12.01; break;
                             case 'H' : count += 1.008; break;
                             case 'O' : count += 16.00; break;
                             case 'N' : count += 14.01; break;
                         }
                 }
             }
         }
         cout << fixed << setprecision() << count << endl;
     }
     return ;
 }