题解 | #HJ063 DNA序列#

import java.util.Scanner;

/**
 * HJ63 DNA序列 -中等
 */
public class HJ063 {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        while (sc.hasNext()) {
            String str = sc.next();
            int num = sc.nextInt();
            String CGRate = getCGRate1(str, num);
            System.out.println(CGRate);
        }
        sc.close();
    }

    public static String getCGRate1(String str, int num) {
        int max = 0;
        int subBegin = 0;
        for (int i = 0; i <= str.length() - num; i++) {
            int cgCount = 0;
            // 遍历统计CG个数
            for (int j = 0; j < num; j++) {
                if (str.charAt(i + j) == 'C'
                        || str.charAt(i + j) == 'G') {
                    cgCount++;
                }
            }
            // CG个数大于历史最高，记录截取开始位置
            if (cgCount > max) {
                max = cgCount;
                subBegin = i;
            }
        }
        String CGRate = str.substring(subBegin, subBegin + num);
        return CGRate;
    }
}