UVa 1586

识别化学式，然后计算总值

#include <cstdio>
#include <iostream>
#include <cstring>
using namespace std;
double a[5]={0,12.01,1.008,16.00,14.01};
char s[105];
int t,len,cnt;
double ans,tmp;
void fuc(){
    ans=0; cnt=1;
    for(int i=0;i<len;i++){
        if(s[i]=='C') tmp=a[1];
        else if(s[i]=='H') tmp=a[2];
        else if(s[i]=='O') tmp=a[3];
        else if(s[i]=='N') tmp=a[4];
        else {
            cnt*=(s[i]-'0');
            while(s[i+1]<='9'&&s[i+1]>='0'){
                i++;
                cnt*=10;
                cnt+=(s[i]-'0');
            }
        }
        if(s[i+1]>'9'||s[i+1]<'0'){
            ans+=tmp*cnt;
            cnt=1;
        }
    }
}
int main(){
    scanf("%d",&t);
    while(t--){
        scanf("%s",s);
        len=strlen(s);
        fuc();
        printf("%.3lf
",ans);
    }
}