Molar mass UVA – 1586

题解：已知元素组成求解相对分子量，单个元素最多只有两位数两层if判断就可以了

#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
const int n=256;
const int maxn=10001;
double mass[n];


int  main()
{
    memset(mass,0,256);
    mass['C']=12.01;
    mass['H']=1.008;
    mass['O']=16.00;
    mass['N']=14.01;
    int t;
    cin>>t;
    while(t--)
    {
        string str;
        cin>>str;
        double sum = 0;
        double temp;
        for(int i=0; i<str.size(); i++){
            if(mass[str[i]]){
                    if(str[i+1]>='1'&&str[i+1]<='9'){
                        if(str[i+2]>='0'&&str[i+2]<='9'){
                            temp=(str[i+1]-'0')*10+str[i+2]-'0';
                            sum +=temp*mass[str[i]];
                            i+=2;
                        }
                        else{
                            temp=str[i+1]-'0';
                            sum +=temp*mass[str[i]];
                            i++;
                        }
                    }
                    else{
                        sum +=mass[str[i]];
                    }
                }
        }
        printf("%.3f
",sum);
    }

    return 0;
}