题解 | #DNA序列#

import java.util.Scanner;

// 题目不难 关键理解GC-Ratio是什么东西！我做了36分钟，罪过
public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        String s = in.nextLine();
        int n = in.nextInt();
        int ratio = 1;
        String ratioStr = "";
        
        for(int i=0; i<s.length() - n + 1; i++) {
            String sub = s.substring(i, i+n);
            if(sub.indexOf("C")>=0 && sub.indexOf("G")>=0) {
                String temp = sub.replace("C","").replace("G","");
                if(n - temp.length() > ratio) {
                    ratioStr = sub;
                    ratio = n - temp.length();
                }
            }
        }
        System.out.println(ratioStr);
    }
}