UVA1586 Molar mass @ K_程式人

https://uva.onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&page=show_problem&problem=4461

#include <iostream>

#include <iomanip>

using namespace std;

int main()
{
   double numC=12.01;
   double numH=1.008;
   double numO=16.00;
   double numN=14.01;
   int T;
   string s;
   cin>>T;
   while(T--)
   {
       double sum=0,temp=0;
       cin>>s;
       for(int i=0;i<s.length();i++)
       {
           if(isalpha(s[i]))
           {
               switch(s[i])
               {
                   case 'C':
                       temp=numC;
                       break;
                   case 'H':
                       temp=numH;
                       break;
                   case 'O':
                       temp=numO;
                       break;
                   case 'N':
                       temp=numN;
                       break;
               }
               if(isalpha(s[i+1]) || s[i+1]=='\0')
               {
                   sum+=temp;
               }
           }
           if(isdigit(s[i]))
           {
               if(s[i+1]=='\0' || isalpha(s[i+1]))
               {
                   int n=(int)s[i];
                   n=n-48;
                   sum+=(temp*n);
               }
               else if(isdigit(s[i+1]))
               {
                   int n=(int)s[i];
                   n=n-48;
                   sum+=(temp*n*10);
               }
           }
       }
       cout<<fixed<<setprecision(3)<<sum<<endl;
   }
}