PAT 1041 Be Unique

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]. 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 (≤) 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

#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
#define MAXN 100005

int a[MAXN];



int main(){
    int n;cin >> n;
    map<int,int>mp;
    for(int i=0;i < n;i++){cin >> a[i];mp[a[i]]++;}
    int flag = 1;
    for(int i=0;i < n;i++){
        if(mp[a[i]] == 1){cout << a[i];flag=0;break;}
    }
    if(flag) cout << "None";
    return 0;
}

我，水题之王