UVa 1586 Molar mass

#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
using namespace std;

char s[1005];
double yuansu[5];

int main()
{
int ncase,i,ans,len;
double tmp=0;
scanf("%d",&ncase);
yuansu[2]=12.01;
yuansu[7]=1.008;
yuansu[14]=16.00;
yuansu[13]=14.01;
while(ncase--)
{
cin>>s;
len=strlen(s);
tmp=0;
for(i=0;i<len;i++)
{
ans=0;
if(isalpha(s[i]))
{
if(isdigit(s[i+2])&&isdigit(s[i+1]))
ans+=s[i+2]-'0'+(s[i+1]-'0')*10;
else if(isdigit(s[i+1]))
ans+=s[i+1]-'0';
else
ans=1;
}
tmp+=ans*1.0*yuansu[s[i]-'A'];
}
printf("%.3lf\n",tmp);
}
}