题解 | #DNA序列#正则

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 in = new Scanner(System.in);
        // 注意 hasNext 和 hasNextLine 的区别
        while (in.hasNextLine()) { // 注意 while 处理多个 case
            String str = in.nextLine();
            int n = Integer.valueOf(in.nextLine());
            double finalRatio = 0.0000;
            String res = str;
            for (int l = 0; l < str.length() - n; l++) {
                String son = str.substring(l, l + n);
                String temp = son.replaceAll("[G,C]", "");
                double ratio = (n - temp.length()) * 1.0000 / n;
                if (ratio > finalRatio) {
                    finalRatio = ratio;
                    res = son;
                }
            }
            System.out.println(res);
        }
    }
}