#include<algorithm>
#include<iostream>//Header file needed to use unique
using namespace std;

int n;

int main(){
    cin>>n;
    vector<int> res;
    while(n--){
        int a;
        cin>>a;
        res.push_back(a);
    }
    sort(res.begin(),res.end());
    vector<int>::iterator it = unique(res.begin(),res.end());
    res.erase(it,res.end());

    cout<<res.size()<<endl;
    for(auto t:res)cout<<t<<' ';
    puts("");
}

改进前

#include<algorithm>
#include<iostream>
using namespace std;

const int N = 1010;
bool flag[N];

int n;

int main(){
    cin>>n;
    vector<int> res;
    while(n--){
        int a;
        cin>>a;
        if(!flag[a]){
            res.push_back(a);
            flag[a]=true;
        }
    }
    sort(res.begin(),res.end());
    cout<<res.size()<<endl;
    for(auto t:res)cout<<t<<' ';
    puts("");
}

生成随机数 非题解

#include<iostream>
#include<ctime>//Header file needed to use time
#include<cstdlib>//Header file needed to use srand,rand
#include<vector>//Header file needed to use vector
#include<algorithm>//Header file needed to use sort
using namespace std;

const int N = 1010;
int n;
int maxValue=100;
int minValue=1;


int flag[N];

int main(){
    cin>>n;
    cout<<n<<endl;
    vector<int> res;
    unsigned send=time(0);
    srand(send);
    for(int i =0;i<n;i++){
        int rom = rand()%(maxValue-minValue+1)+minValue;
        //res.push_back(rom);
        if(!flag[rom]){
            res.push_back(rom);
            flag[rom]=true;
        }else{
            i--;
        }

    }
    sort(res.begin(),res.end());
    for(auto t:res)cout<<t<<' ';
    puts("");

}