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 {
    static Boolean Check(char a){
        if(a =='C'|| a =='G'){
            return true;
        }else {
            return false;
        }
    }
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        String s = in.nextLine();
        int n = in.nextInt();
        int num = 0;
        int max = 0;
        int l = 0;
        int r = n-1;
        int resl = 0;
        String first = s.substring(0,n);
        for(int i = 0;i < first.length();i++){
            char e = first.charAt(i);
            if(Check(e)){
                num++;
            }
        }
        max = num;
        while(l < s.length()-n){
            if(Check(s.charAt(l))){
                num--;
            }
            if(Check(s.charAt(r+1))){
                num++;
            }
            if(num > max){
                max = num;
                resl = l+1;
            }
            l++;
            r++;

        }
        System.out.println(s.substring(resl,resl+n));

    }
}