C++ :

#include <bits/stdc++.h>
using namespace std;
int a[30],n,r,b[30];

void dfs(int x,int cnt){
    if(cnt == r){
        for(int i = 1;i <= r;i++){
            cout<<b[i]<<" ";
        }
        cout<<endl;
        return;
    }
    if(x > n) return;
    b[cnt + 1] = a[x];
    dfs(x+1,cnt+1);
    dfs(x+1,cnt);
}

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