题解 | #DNA序列#

import java.util.Scanner;

public class Main {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        String dna = sc.nextLine();
        int l = sc.nextInt();
        int gcMax = 0;
        int gcMaxIndex = 0;
        for (int i = 0; i < dna.length()-l; i++) {
            int j = i;
            int gcCount = 0;
            while(j < i+l){
                char c = dna.charAt(j);
                if(c=='G' || c=='C'){
                    gcCount++;
                }
                j++;
            }
            if(gcCount > gcMax){
                gcMax = gcCount;
                gcMaxIndex = i;
            }
        }
        for (int i = gcMaxIndex; i < gcMaxIndex+l; i++) {
            System.out.printf(String.valueOf(dna.charAt(i)));
        }
    }
}