pat 1041 Be Unique（20 分）

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​​]. 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 (≤10​5​​) 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 <iostream>
#include <algorithm>
#include <cstdio>
#include <cstring>
#include <map>
#include <stack>
#include <vector>
#include <queue>
#include <set>
#define LL long long
using namespace std;
const int MAX = 1e5 + 10;

map <int, int> mp;
map <int, int> :: iterator iter;
int n, a, A[MAX];

int main()
{
//    freopen("Date1.txt", "r", stdin);
    scanf("%d", &n);
    for (int i = 0; i < n; ++ i)
    {
        scanf("%d", &a);
        A[i] = a;
        mp[a] ++;
    }

    for (int i = 0; i < n; ++ i)
    {
        if (mp[A[i]] == 1)
        {
            printf("%d\n", A[i]);
            return 0;
        }
    }
    printf("None\n");
    return 0;
}