Question

Can someone tell me why the variable percent = 0? It should be 33.3333 right? (2/6)

because when I run the function below, the result are

Total lines = 6
Odd lines = 2
Percent odd lines = 0

bool count_odd_lines(string a, string b)
{
    ifstream in;
    ofstream out;
    in.open(a.c_str());
    out.open(b.c_str()); 
    string s;
    int count = 0;
    int odd =  0;  
    if (in && out)
    {
        while (getline(in, s))
        {
            count++;
            if (s.length() % 2 != 0) odd++;
        }
        out << "Total lines = " << count << endl;
        out << "Odd lines = " << odd << endl;
        double percent = odd/count;
        out << "Percent odd lines = " << setprecision(4) << percent <<endl;
        return true;
    }
    else return false; 
    in.close();
    out.close();
}

Answer 1

There are two issues:

1. Both odd and count are integer, so odd/count performs integer (that is, truncating) division.
2. To get a percentage (i.e. 33.33 rather than 0.3333) you need to multiply the result by 100.

You can fix both issues like so:

double percent = odd * 100.0 / count;

The multiplication does the scaling and also turns the subsequent division into a floating-point one.