1041. Be Unique (20)

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

#include <iostream>
#include <vector>
using namespace std;
int main()
{
int n;
cin>>n;
vector<int> unique(10001);
vector<int> vec(n);
for(int i=0;i<n;i++)
{
cin>>vec[i];
unique[vec[i]]++;
}
bool exist=false;
for(int i=0;i<n;i++)
{
if(unique[vec[i]] == 1)
{
exist=true;
cout<<vec[i]<<endl;
break;
}
}
if(exist == false)
cout<<"None\n";
return 0;
}