Find the k permutations of n items.

Kperm.java

import java.io.*;
import java.util.*;

public class Kperm {
    static void kperm(List<Integer> items, int k) {
        kperm(items, new ArrayList<Integer>(), k);
    }

    static void kperm(List<Integer> items, List<Integer> accum, int k) {
        if (accum.size() == k) {
            System.out.println(accum);
            return;
        }
        for (int i = 0; i < items.size(); ++i) {
            int item = items.get(i);
            List<Integer> newItems = new ArrayList<>();
            newItems.addAll(items.subList(0,i));
            newItems.addAll(items.subList(i+1,items.size()));
            accum.add(item);
            kperm(newItems, accum, k);
            accum.remove(accum.size()-1);
        }
    }
    
    public static void main(String[] args) {
        kperm(Arrays.asList(1,2,3,4,5), 3);
    }
}