C++ :

#include<iostream>
#include<cstring>
#include<cstdio>
using namespace std;
int n,t,fm=0,sum=0;;
bool f[1001];
int main()
{
	memset(f,0,sizeof(f));
	scanf("%d",&n);
	for(int i=1;i<=n;++i){scanf("%d",&t);if(!f[t]){f[t]=1;sum++;};if(t>fm)fm=t;}
	printf("%d\n",sum);
	for(int i=1;i<=fm;++i)
	  if(f[i]){if(i==fm)printf("%d\n",fm);else printf("%d ",i);}
	return 0;
}

Pascal :

var
  n,x,i,s:integer;
  a,b:array[1..1000]of integer;
begin
	readln(n);
	for i:=1 to n do begin
		read(x);
		a[x]:=1;
	end;
	s:=0;
	for i:=1 to 1000 do s:=s+a[i];
	writeln(s);
	x:=0;
	for i:=1 to 1000 do
		if a[i]>0 then begin inc(x);b[x]:=i; end;
	for i:=1 to s-1 do write(b[i],' ');write(b[s]);
end.

Java :

import java.util.Arrays;
import java.util.HashSet;
import java.util.Scanner;
import java.util.Set;

public class Main {
    public static void main(String[] args) {
        Scanner cin = new Scanner(System.in);
        while (cin.hasNext()) {
            int size = cin.nextInt();
            Set<Integer> sets = new HashSet<Integer>();
            for (int i = 0; i < size; i++) {
                sets.add(cin.nextInt());
            }

            Integer[] nums = new Integer[sets.size()];
            sets.toArray(nums);
            Arrays.sort(nums);
            System.out.println(nums.length);
            for (int i = 0; i < nums.length; i++) {
                System.out.print(nums[i]);
                if (i < nums.length -1) {
                    System.out.print(" ");
                }
            }
        }
    }
}