分子量（UVa1586）

　　题目具体描述见：https://uva.onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&category=830&page=show_problem&problem=4461

C++11代码如下：

 #include<iostream>
 #include<string.h>
 #include<iomanip>
 using namespace std;
 #define maxn 85
 char s[maxn];

 int main() {
     int T;
     cin >> T;
     while (T--) {
         int num_c = , num_h = , num_o = , num_n = ;  //分别记录各个化学元素的个数
         float sum = 0.0;
         cin >> s;
         int n = strlen(s);
         s[n] = ;
         for (int i = ; i < n; i++) {
             if (isalpha(s[i])) {  //判断是否是字母
                 switch (s[i]) {
                 case 'C':if (isdigit(s[i + ])) {  //判断字母后面2位是否为数字
                             if (isdigit(s[i + ])) num_c += (s[i + ] - '') *  + (s[i + ] - '');
                             else num_c += (s[i + ] - '');
                          }
                          else num_c++; break;
                 case 'H':if (isdigit(s[i + ])) {
                             if (isdigit(s[i + ])) num_h += (s[i + ] - '') *  + (s[i + ] - '');
                             else num_h += (s[i + ] - '');
                          }
                          else num_h++; break;
                 case 'O':if (isdigit(s[i + ])) {
                             if (isdigit(s[i + ])) num_o += (s[i + ] - '') *  + (s[i + ] - '');
                             else num_o += (s[i + ] - '');
                          }
                          else num_o++; break;
                 case 'N':if (isdigit(s[i + ])) {
                             if (isdigit(s[i + ])) num_n += (s[i + ] - '') *  + (s[i + ] - '');
                             else num_n += (s[i + ] - '');
                          }
                          else num_n++; break;
                 default:break;
                 }
             }
             else continue; //当前数组元素为数字，则直接进入下次循环
         }
         sum = 12.01*num_c + 1.008*num_h + 16.00*num_o + 14.01*num_n;
         cout << fixed<<setprecision()<<sum << endl;  //小数点后面保留三位数字
     }

     return ;
 }