count_nucleotides.cpp

#include <iostream>
#include <string>
using namespace std;

int main()
{
    //define variable s as DNA string
    string s;

    // get input from stdin
    cin >> s;

    // define counts of nucleotides
    int a=0, c=0, g=0, t=0;

    // define n as current nucleotide
    char n;

    // loop through elements of DNA string
    for (int i=0; i<s.length(); ++i)
    {
        n = s[i];

        if (n == 'A')
        {
            a++;
        }
        if (n == 'C')
        {
            c++; // wahey
        }
        if (n == 'G')
        {
            g++;
        }
        if (n == 'T')
        {
            t++;
        }
    }
    // output to stdout
    cout << a <<" "<< c <<" "<< g <<" "<< t << endl;
    return 0;
}