题解 | #DNA序列#

#include <iostream>
#include <string>

using namespace std;

int main()
{
    string str;
    cin>>str;

    int num;
    cin>>num;
    int length = str.length();

    string result;
    double rate = 0;
    if(length == num)
    {
        cout<<str<<endl;
        return 0;
    }
    for(int i=0; i<length-num; i++)
    {
        //get substring
        string sub = str.substr(i,num);
        int tmp = 0;
        for(int j=0; j<num; j++)
        {
            if(sub[j] == 'G' || sub[j] == 'C')
            {
                tmp++;
            }
        }
        if(rate < (double)tmp/(double)num)
        {
            rate =  (double)tmp/(double)num;
            result = "";
            result = sub;
        }
    }
    cout<<result<<endl;
    return 0;
}