acwing1204

题解：

import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		int[] arr = new int[100005];
		Scanner in = new Scanner(System.in);
		int N = Integer.parseInt(in.nextLine());
        //此处不能用in.nextIN(),否则下面的nextLine会读入上面一行结尾的回车符
		int min = 100005, max = 0;
		while (N != 0) {
			N--;
			String[] str = in.nextLine().split("\\s+");
            //split里的正则表达式可以将一个字符串拆穿成一个字符数组
            //这里的\\s表示若干空格
			for (int i = 0; i < str.length; i++) {
				int index = Integer.parseInt(str[i]);
                //静态方法pareseInt可以将字符串转换为数字
				arr[index]++;
				min = Math.min(min, index);
				max = Math.max(max, index);
			}
		}
		int n = 0, m = 0;
		for (int i = min; i <= max; i++) {
			if (arr[i] == 0)
				m = i;
			if (arr[i] == 2)
				n = i;
		}
		System.out.println(m + " " + n);
		in.close();

	}

}

也可以使用BufferedReader（效率更高，推荐）：

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class No_1204 {

	public static void main(String[] args) throws IOException {
		int[] arr = new int[100005];
		BufferedReader bf = new BufferedReader(new InputStreamReader(System.in));
		int N = Integer.parseInt(bf.readLine());
		int min = 100005, max = 0;
		while (N != 0) {
			N--;
			String[] str = bf.readLine().split("\\s+");
			for (int i = 0; i < str.length; i++) {
				int index = Integer.parseInt(str[i]);
				arr[index]++;
				min = Math.min(min, index);
				max = Math.max(max, index);
			}
		}
		int n = 0, m = 0;
		for (int i = min; i <= max; i++) {
			if (arr[i] == 0)
				m = i;
			if (arr[i] == 2)
				n = i;
		}
		System.out.println(m + " " + n);
		bf.close();

	}

}