3900 - Molar mass Asia - Seoul - 2007/2008

3900 - Molar mass Asia - Seoul - 2007/2008
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An organic compound is any member of a large class
of chemical compounds whose molecules contain carbon. The molar mass of an organic compound is the mass of one mole of
the organic compound. The molar mass of an organic compound can be computed from
the standard atomic weights of the elements.

 



When an organic compound is given as a molecular
formula, Dr. CHON wants to find its molar mass. A molecular formula, such
as C3
H4
O3
, identifies each constituent element by its chemical
symbol and indicates the number of atoms of each element found in each discrete
molecule of that compound. If a molecule contains more than one atom of a
particular element, this quantity is indicated using a subscript after the
chemical symbol.

In this problem, we assume that the molecular formula is represented by only
four elements, `C' (Carbon), `H' (Hydrogen), `O'
(Oxygen), and `N' (Nitrogen) without parentheses.

The following table shows that the standard atomic weights for `C',
`H', `O', and `N'.

 

Atomic Name	Carbon	Hydrogen	Oxygen	Nitrogen
Standard Atomic Weight	12.01 g/mol	1.008 g/mol	16.00 g/mol	14.01 g/mol

 

For example, the molar mass of a molecular formula C6 H5 OH is 94.108
g/mol which is computed by 6 ×
(12.01 g/mol) + 6 ×
(1.008 g/mol) + 1 ×
(16.00 g/mol).

Given a molecular formula, write a program to compute the molar mass of the
formula.

 

Input 

Your program is to read from standard input. The input consists of T test cases. The number of
test cases T is given in
the first line of the input. Each test case is given in a single line, which
contains a molecular formula as a string. The chemical symbol is given by a
capital letter and the length of the string is greater than 0 and less than 80.
The quantity number n
which is represented after the chemical symbol would be
omitted when the number is 1 (2

n

99) .

 

Output 

Your program is to write to standard output. Print exactly one line for each
test case. The line should contain the molar mass of the given molecular
formula.

 

Sample
Input 

 

4
C
C6H5OH
NH2CH2COOH
C12H22O11

 

Sample
Output 

 

12.010
94.108
75.070
342.296

 

Seoul 2007-2008

#include<iostream>
#include<cstdio>
#include<cctype>
#include<string>
using namespace std;
int main()
{
int T;
scanf("%d",&T);
while(T--)
{
string s;
cin>>s;
int len=s.size();
int num=0;
int c=0,h=0,o=0,n=0;
double sum=0;
if(len==1)
{
if(s[0]=='C')  c++;
else if(s[0]=='H')  h++;
else if(s[0]=='O')  o++;
else n++;
}
else
{
for(int i=0; i<len; i++)
{
if(isalpha(s[i]))
{
if(num==0)  num++;
else
{
if(s[i-1]=='C')  c++;
else if(s[i-1]=='H')  h++;
else if(s[i-1]=='O')  o++;
else n++;
}
}
else
{
int kk=s[i]-'0';
bool flag=false;
if(i<len-1&&isdigit(s[i+1]))
{
kk=kk*10+s[i+1]-'0';
flag=true;
}
if(s[i-1]=='C')  c+=kk;
else if(s[i-1]=='H')  h+=kk;
else if(s[i-1]=='O')  o+=kk;
else n+=kk;
num=0;
if(flag)  i++;
}
}
}
if(num!=0)
{
if(s[len-1]=='C')  c++;
else if(s[len-1]=='H')  h++;
else if(s[len-1]=='O')  o++;
else n++;
}
sum=12.01*c+1.008*h+16.00*o+14.01*n;
printf("%0.3lf/n",sum);
}
return 0;
}