题解 | #DNA序列#

import java.util.Scanner;

// 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.hasNextLine()) {
            String s = sc.nextLine();
            int split = Integer.parseInt(sc.nextLine());
            int maxIndex = 0;
            int maxCnt = 0;
            for (int i = 0; i < s.length() - split; i++) {
                int cnt = countCAndG(s.substring(i, i + split));
                if (cnt > maxCnt) {
                    maxCnt = cnt;
                    maxIndex = i;
                }
            }
            System.out.println(s.substring(maxIndex, maxIndex + split));
        }
    }

    private static int countCAndG(String sub) {
        char[] chs = sub.toCharArray();
        int count = 0;
        for (int i = 0; i < chs.length; i++) {
            if (chs[i] == 'C' || chs[i] == 'G') {
                count++;
            }
        }
        return count;
    }
}