chaper3_exerise_Uva1568_Molar_Mass_分子量

#include<iostream>
#include<iomanip> 
#include<string>
#include<cctype>
using namespace std;
const int maxn = 1010;

void get_num(int &num,string c,int j)
{
    while (isdigit(c[j]) && c[j])
    {
        num = num*10 + (c[j]-'0');
        j++;
    }
}

int main(void)
{
    string c;
    int T;
    cin >> T;
    for (int i = 0; i < T; i++)
     {
         double count = 0;
         cin >> c;
        for (int j = 0; j < c.size(); j++)
        {
            if (isalpha(c[j]))
            {
                if (isdigit(c[j+1]))
                {
                    int num = 0;
                    get_num(num,c,j+1); 
                    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(3) << count << endl;
    }
    return 0;
}