题解

真的超简单，感觉配不上黄题
不过最开始粗心了，没注意还要输出个数

#include <bits/stdc++.h>
using namespace std;
int main() {
    map<int, int> m;
    int n, a[105];
    cin >> n;
    int tmp = n;
    for (int i = 1; i <= n; i++) {
        cin >> a[i];
        m[a[i]]++;
        if (m[a[i]] > 1) {
            tmp--;
            m[a[i]]--;
        }
    }
    sort (a + 1, a + n + 1);
    cout << tmp << endl;
    for (int i = 1; i <= n; i++) if (a[i] != a[i - 1]) cout << a[i] << " ";
}