Be Unique (20)

import java.io.PrintStream;
import java.text.ParseException;
import java.util.HashMap;
import java.util.LinkedList;
import java.util.List;
import java.util.Scanner;

public class Main {
	public static Scanner in = new Scanner(System.in);
	public static PrintStream out = System.out;

	public static void main(String[] args) throws ParseException {
		int N = in.nextInt();
		int bet;

		// list存储可能的结果值
		List<Integer> list = new LinkedList<>();
		HashMap<Integer, Integer> map = new HashMap<>();

		for (int i = 0; i < N; ++i) {
			bet = in.nextInt();
			Integer val = map.get(bet);
			if (val == null) {
				map.put(bet, 1);
				list.add(bet);
			} else {
				map.put(bet, val + 1);
			}
		}

		// 检测list存储的值是否符合要求
		boolean findWinner = false;
		for (int i = 0; i < list.size(); ++i) {
			if (map.get(list.get(i)) == 1) {
				out.println(list.get(i));
				findWinner = true;
				break;
			}
		}
		if (!findWinner) {
			out.println("None");
		}
	}
}