题解 | 游游的字母翻倍

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);
        int number1 = in.nextInt();
        int number2 = in.nextInt();
        StringBuilder letters = new StringBuilder(in.next());

	  //从后向前遍历，为了避免在插入字符后影响尚未遍历到的索引位置。
        for (int i = 0; i < number2; i++) {
            int begin = in.nextInt();;
            int end = in.nextInt();
            for (int j = end; j >= begin ; j--) {
                char c = letters.charAt(j - 1);
                letters.insert(j, c);
            }
        }
        System.out.println(letters.toString());
    }
}