1041. Be Unique (20) PAT 甲级

#include<stdio.h>

int HashTable[10010];
int a[100010];

int main(){
int N;
int count=0;
scanf("%d",&N);
for(int i=0;i<N;i++){
scanf("%d",&a[i]);
HashTable[a[i]]++;
}

for(int i=0;i<N;i++){
if(HashTable[a[i]]==1)
{
printf("%d",a[i]);
count++;
break;
}
}
if(count==0)    printf("None\n");
return 0;
}