1041 Be Unique （20 分）

Being unique is so important to people on Mars that even their lottery is designed in a unique way. The rule of winning is simple: one bets on a number chosen from [1, $10^4$

10^4 ]. The first one who bets on a unique number wins. For example, if there are 7 people betting on { 5 31 5 88 67 88 17 }, then the second one who bets on 31 wins.

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Input Specification:
Each input file contains one test case. Each case contains a line which begins with a positive integer N (≤ $1$

0 5 10^5 ) and then followed by N bets. The numbers are separated by a space.

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Output Specification:
For each test case, print the winning number in a line. If there is no winner, print None instead.

Sample Input 1:

7 5 31 5 88 67 88 17

Sample Output 1:

31

Sample Input 2:

5 888 666 666 888 888

Sample Output 2:

None

解析

找第一個unique的數字。最簡單的方法：開一個arr[ $10^4+1$]的數字。把每個數字出現的次數+1。
最後就挨個遍歷輸入的數字：看出現的次數是不是1.

#include<iostream>
#include<string>
#include<vector>
#include<algorithm>
#include<map>
using namespace std;
int main()
{
	int N;
	scanf("%d", &N);
	vector<int> data(N,0);
	for (int i = 0; i < N; i++) 
		scanf("%d", &data[i]);
	map<int, int> Map;
	for (auto x : data)
		Map[x]++;
	vector<int> Unique;
	for (auto x : Map) {
		if (x.second == 1)
			Unique.push_back(x.first);
	}
	if (Unique.empty())
		printf("None");
	else {
		for (auto& x : Unique)
			x = find(data.cbegin(), data.cend(), x) - data.cbegin();
		printf("%d", data[*min_element(Unique.cbegin(), Unique.cend())]);
	}
}