题解 | A7831.小码君的随机数

#include <bits/stdc++.h>
using namespace std;
int n , a[1005];
int main(){
	cin >> n;
    for(int i = 1;i <= n;i++){
        int m;
        cin >> m;
        a[m]++;
    }
    int sum = 0;
    for(int i = 1;i <= 1000;i++){
        if(a[i] != 0){
            sum ++;  
        }
    }
    cout << sum << "\n";
    for(int i = 1;i <= 1000;i++){
        if(a[i] != 0){
            cout << i << " "; 
        }
    }
    return 0;
}