问题 C: Be Unique (20)

题目描述

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.

输入

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.

输出

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

样例输入

7 5 31 5 88 67 88 17
5 888 666 666 888 888

样例输出

31
None

思路

题目的意思是：找到一组数中第一个只出现一次的数。

#include
using namespace std;
int main()
{
    int n;
    while(cin >> n)
    {
        vectorres(n);
        unordered_mapmp;
        setst;
        for(int i=0; i> res[i];
            mp[res[i]] ++;
            st.insert(res[i]);
        }
        int flag = 0;
        for(int i=0; i