题解 | #DNA序列#

import java.util.Scanner;
import java.util.ArrayList;
import java.util.List;
// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        while (sc.hasNext()){
                String str = sc.nextLine();
                String nn = sc.nextLine();
                int n = Integer.parseInt(nn);

                List<String> alist = new ArrayList<>();
                for (int j = 0; j < str.length(); j++) {//abcde
                    for (int k = str.length(); k > j; k--) {
                        alist.add(str.substring(j,k));
                    }
                }

                List<String> list = new ArrayList<>();
                for (String temp:alist
                     ) {
                    if (temp.length()==n){
                        list.add(temp);
                    }
                }

                double temp = 0.0;
                int index = 0;
                for (int j = 0; j < list.size(); j++) {
                    String str1 = list.get(j);
                    double Glen = str1.length()-str1.replaceAll("G","").length();
                    double Clen = str1.length()-str1.replaceAll("C","").length();
                    double GC = (Glen + Clen)/str1.length();
                    if (GC>temp){
                        temp = GC;
                        index = j;
                    }
                }
                System.out.println(list.get(index));

        }
    }
}