1041 Be Unique (20 分)（简单模拟，出现次数统计）

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

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#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
const int N=1e5+5;
int a[N],num[N];
int main(){
    int n;
    scanf("%d",&n);
    for(int i=1;i<=n;i++){
    	scanf("%d",&a[i]);
    	num[a[i]]++;
    } 
    bool flag=false;
    for(int i=1;i<=n;i++){
    	if(num[a[i]]==1){
    	   printf("%d\n",a[i]);
    	   flag=true;
    	   break;
	}
    }
    if(!flag) printf("None\n");
    return 0;
}