python/TangDou/CSP-J/AcWingTraining/T6/TD1.cpp

#include <bits/stdc++.h>

using namespace std;
int n, k;
const int N = 110;
int a[N];
bool st[N];
vector<int> res;
/*
4 2
1 1 2 3
*/
void dfs(int u, int k) {
    if (k == 0) {
        for (int i = 0; i < res.size(); i++)
            cout << res[i] << " ";
        cout << endl;
        return;
    }
    if (u == n + 1) return;

    if (a[u - 1] == a[u] && st[a[u - 1]] == 0) {
        dfs(u + 1, k);
    } else {
        st[a[u]] = 1;
        res.push_back(a[u]);
        dfs(u + 1, k - 1);
        res.pop_back();
        st[a[u]] = 0;
        dfs(u + 1, k);
    }
}

int main() {
    cin >> n >> k;
    for (int i = 1; i <= n; i++) cin >> a[i];
    sort(a + 1, a + 1 + n);
    dfs(1, k);
    return 0;
}