PAT--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 <bits/stdc++.h>
#include <cstring>
using namespace std;
int flag[10001];
int main()
{
    int n;
    cin>>n;
    int a[n];
    memset(flag,0,sizeof(flag));

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

 分析：

桶排序的变形