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, 10⁴]. 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.

Input Specification:

Each input file contains one test case. Each case contains a line which begins with a positive integer N (<=10⁵) and then followed by N bets. The numbers are separated by a space.

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

思路
和1084差不多的思路，队列q记录顺序，字典dic记录是否重复出现。遍历q的时候查下字典，输出第一个满足"仅出现一次"的数字即可。
代码

#include<iostream>

#include<map>

#include<iterator>

#include<queue>

using namespace std;

int main()

{

   int N;

   while(cin >> N)

   {

       map<int,int> dic;

       queue<int> q;

       for(int i = ;i < N;i++)

       {

           int value;

           cin >> value;

           if(dic.count(value) > )

             dic[value] = -;

           else

           {

              q.push(value);

              dic.insert(pair<int,int>(value,));

           }

       }

       bool check = false;

       while(!q.empty())

       {

           if(dic[q.front()] > )

           {

             check = true;

             cout << q.front();

             break;

           }

           q.pop();

       }

       if(!check)

         cout << "None" << endl;

   }

}