PAT (Advanced Level) 1041. Be Unique (20)

简单题。

#include<cstdio>
#include<cstring>
#include<cmath>
#include<vector>
#include<map>
#include<queue>
#include<stack>
#include<string>
#include<algorithm>
using namespace std;

int n;
int a[+];
int f[+];

int main()
{
    memset(f,,sizeof f);
    scanf("%d",&n);
    for(int i=;i<=n;i++) scanf("%d",&a[i]);
    for(int i=;i<=n;i++) f[a[i]]++;
    int fail=;
    for(int i=;i<=n;i++)
    {
        if(f[a[i]]==)
        {
            fail=;
            printf("%d\n",a[i]);
            break;
        }
    }
    if(fail==) printf("None\n");
    return ;
}