输入：
```plain
2
1 1
```
行首会多输出一个空格。
by Disjoint_cat @ 2023-12-31 17:29:58
```cop
#include<bits/stdc++.h>
using namespace std;
int a[1005],b[1005],f[1005];
int main(){
int n;
scanf("%d",&n);
for(int i=1;i<=n;i++){
scanf("%d",&a[i]);
f[a[i]]++;
}
int cnt=0;
for(int i=1;i<=1000;i++)
if(f[i]>=1)
{
cnt++;
b[cnt]=i;
}
printf("%d\n",cnt);
for(int i=1;i<=1000;i++)
{
if(i==cnt)
{
printf("%d",b[i]);
return 0;
}
else
printf("%d ",b[i]);
}
return 0;
}
by wangshuhang @ 2024-01-29 15:26:19