com.github.javachat.streems.spliterators.BreadthFirstSpliterator Maven / Gradle / Ivy

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package com.github.javachat.streems.spliterators;

import java.util.ArrayDeque;
import java.util.Collections;
import java.util.Deque;
import java.util.Iterator;
import java.util.function.Consumer;
import java.util.function.Function;

/**
 * A spliterator for breadth-first traversal
 *
 * @param  type of the nodes in the tree
 */
public final class BreadthFirstSpliterator
    extends NaryTreeSpliterator
{
    private final Deque> deque = new ArrayDeque<>();

    public BreadthFirstSpliterator(final T root,
        final Function> fn)
    {
        super(root, fn);
        deque.addFirst(Collections.singleton(root).iterator());
    }

    @SuppressWarnings("TailRecursion")
    @Override
    public boolean tryAdvance(final Consumer action)
    {
        Iterator iterator;
        T element;

        while (!deque.isEmpty()) {
            iterator = deque.getFirst();
            if (!iterator.hasNext()) {
                deque.removeFirst();
                continue;
            }
            element = iterator.next();
            deque.add(fn.apply(element));
            action.accept(element);
            return true;
        }
        return false;
    }
}