题解 | DNA序列

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        char[] chars = sc.nextLine().toCharArray();
        int  k = Integer.parseInt(sc.nextLine());
        int MaxGCNums = 0;
        int GCNums = 0;
        int ans = k - 1;
        for (int i = 0; i < k; i++) {
            if (chars[i] == 'G' || chars[i] == 'C') {
                GCNums++;
            }
        }
        MaxGCNums = GCNums;
        for (int i = k; i < chars.length ; i++) {
            if (chars[i] == 'G' || chars[i] == 'C') {
                GCNums++;
            }
            if (chars[i - k] == 'G' || chars[i - k] == 'C') {
                GCNums--;
            }
            if (GCNums > MaxGCNums) {
                MaxGCNums = GCNums;
                ans = i;
            }
        }
        for (int i = ans - k + 1; i <= ans ; i++) {
            System.out.print(chars[i]);
        }
    }
}