PAT 1041. Be Unique (20)

#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<iostream>
#include<vector>
#include<queue>
#include<algorithm>
using namespace std;
#define maxsize 100001
#define  MIN -10001
int  a[maxsize];
int c[10001]={0};
int main()
{

int n;
scanf("%d",&n);
int j;
for(int i=0;i<n;i++)
{
scanf("%d",&a[i]);
c[a[i]]++;
}
for(j=0;j<n;j++)
if(c[a[j]]==1)
{
printf("%d\n",a[j]);
break;
}
if(j>=n)
printf("None\n");
return 0;
}