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 [1,104]. 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

Sample Solution：

#include <bits/stdc++.h>
using namespace std;
//哈希散列，使用另一个数组存储出现次数，避免进行多次比较，降低时间复杂度
int main(){
    int n;
    int num[100001]={},sum[10001]={};
    cin>>n;
    for(int i=0;i<n;i++){
        cin>>num[i];
        sum[num[i]]++;
    }
    int i=0;
    while(num[i]!=0){
        if(sum[num[i]]==1){
            cout<<num[i];
            return 0;
        }
        i++;
    }
    cout<<"None";
    return 0;
}

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