Main.java Source code

Introduction

Here is the source code for Main.java

Source

//package com.java2s;
import java.util.ArrayList;
import java.util.Collection;
import java.util.List;

public class Main {
    @SafeVarargs
    public static <E> Collection<Collection<E>> cartesianProduct(Collection<E>... collections) {
        // Convert collections to Lists to safely iterate
        List<List<E>> lists = new ArrayList<>(collections.length);
        for (int i = 0; i < collections.length; i++) {
            if (collections[i].isEmpty()) {
                throw new IllegalArgumentException("Input collections must not be empty");
            }
            lists.add(new ArrayList<E>(collections[i]));
        }

        List<Collection<E>> result = new ArrayList<>();
        int[] indexes = new int[collections.length]; // Indexes are initilized to 0 according to the spec
        boolean finished;
        do {
            finished = true;
            List<E> combination = new ArrayList<>();
            for (int i = 0; i < lists.size(); i++) {
                combination.add(lists.get(i).get(indexes[i]));
            }
            result.add(combination);
            for (int i = 0; i < indexes.length; i++) {
                if (indexes[i] < collections[i].size() - 1) {
                    indexes[i]++;
                    finished = false;
                    break;
                }
            }
        } while (!finished);
        return result;
    }
}