用set来做一个桶吧

#include<cstdio>
#include<cstring>
#include<iostream>
#include<set>
using namespace std;
set<int>s;
int n;
int main()
{
	scanf("%d",&n);
	int ta;
	for (int i=1;i<=n;i++)
	{
		scanf("%d",&ta);
		s.insert(ta);
	}
	set<int>::iterator it;
	printf("%d\n",s.size());
	for (it=s.begin();it!=s.end();it++)
		printf("%d ",*it);
	return 0;
}