unique写法

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

const int N = 1010;
int a[N];

int main()
{
    int n;
    cin >> n;
    for(int i = 0; i < n; i ++ ) scanf("%d", &a[i]);
    sort(a, a + n);
    int ans = unique(a, a + n) - a;
    cout << ans;
}

set写法

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

const int N = 1010;
int a[N];

int main()
{
    int n;
    cin >> n;
    set<int> s;
    for(int i = 0; i < n; i ++ )
    {
        scanf("%d", &a[i]);
        s.insert(a[i]);
    }
    cout << s.size();
}