package com.levelup.java.exercises.beginner;
import java.util.Set;
import java.util.stream.Collectors;
import com.google.common.collect.Sets;
/**
* Write a program that generate all combinations of a set returning only that satisfy a size of n.
*
* @author Justin Musgrove
* @see <a href='http://www.leveluplunch.com/java/exercises/combination-generator/'>Combination generator</a>
*/
public class CombinationGenerator {
public static void main(String[] args) {
Set<Integer> general = Sets.newHashSet(1, 2, 3, 4);
Set<Set<Integer>> combinations = generateCombinations(general, 3);
System.out.println(combinations);
}
/**
* Method will generate possible combinations of
* elements based on parameters
*
* @param from
* @param size
*
* @return possible combinations
*
*/
public static Set<Set<Integer>> generateCombinations(
Set<Integer> from,
int size) {
Set<Set<Integer>> elements = Sets.powerSet(from);
Set<Set<Integer>> possibleCombinations = elements.stream().filter(p -> p.size() == size)
.collect(Collectors.toSet());
return possibleCombinations;
}
}
