10888a09821a98ac0680fad765217302858e70fa4Paul Duffin/* 20888a09821a98ac0680fad765217302858e70fa4Paul Duffin * Copyright (C) 2012 The Guava Authors 30888a09821a98ac0680fad765217302858e70fa4Paul Duffin * 40888a09821a98ac0680fad765217302858e70fa4Paul Duffin * Licensed under the Apache License, Version 2.0 (the "License"); 50888a09821a98ac0680fad765217302858e70fa4Paul Duffin * you may not use this file except in compliance with the License. 60888a09821a98ac0680fad765217302858e70fa4Paul Duffin * You may obtain a copy of the License at 70888a09821a98ac0680fad765217302858e70fa4Paul Duffin * 80888a09821a98ac0680fad765217302858e70fa4Paul Duffin * http://www.apache.org/licenses/LICENSE-2.0 90888a09821a98ac0680fad765217302858e70fa4Paul Duffin * 100888a09821a98ac0680fad765217302858e70fa4Paul Duffin * Unless required by applicable law or agreed to in writing, software 110888a09821a98ac0680fad765217302858e70fa4Paul Duffin * distributed under the License is distributed on an "AS IS" BASIS, 120888a09821a98ac0680fad765217302858e70fa4Paul Duffin * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 130888a09821a98ac0680fad765217302858e70fa4Paul Duffin * See the License for the specific language governing permissions and 140888a09821a98ac0680fad765217302858e70fa4Paul Duffin * limitations under the License. 150888a09821a98ac0680fad765217302858e70fa4Paul Duffin */ 160888a09821a98ac0680fad765217302858e70fa4Paul Duffin 170888a09821a98ac0680fad765217302858e70fa4Paul Duffinpackage com.google.common.collect; 180888a09821a98ac0680fad765217302858e70fa4Paul Duffin 190888a09821a98ac0680fad765217302858e70fa4Paul Duffinimport static com.google.common.base.Preconditions.checkNotNull; 200888a09821a98ac0680fad765217302858e70fa4Paul Duffin 210888a09821a98ac0680fad765217302858e70fa4Paul Duffinimport com.google.common.base.Optional; 220888a09821a98ac0680fad765217302858e70fa4Paul Duffin 230888a09821a98ac0680fad765217302858e70fa4Paul Duffinimport java.util.LinkedList; 240888a09821a98ac0680fad765217302858e70fa4Paul Duffinimport java.util.Iterator; 250888a09821a98ac0680fad765217302858e70fa4Paul Duffin 260888a09821a98ac0680fad765217302858e70fa4Paul Duffin/** 270888a09821a98ac0680fad765217302858e70fa4Paul Duffin * A variant of {@link TreeTraverser} for binary trees, providing additional traversals specific to 280888a09821a98ac0680fad765217302858e70fa4Paul Duffin * binary trees. 290888a09821a98ac0680fad765217302858e70fa4Paul Duffin * 300888a09821a98ac0680fad765217302858e70fa4Paul Duffin * @author Louis Wasserman 310888a09821a98ac0680fad765217302858e70fa4Paul Duffin */ 320888a09821a98ac0680fad765217302858e70fa4Paul Duffinpublic abstract class BinaryTreeTraverser<T> extends TreeTraverser<T> { 330888a09821a98ac0680fad765217302858e70fa4Paul Duffin // TODO(user): make this GWT-compatible when we've checked in ArrayDeque and BitSet emulation 340888a09821a98ac0680fad765217302858e70fa4Paul Duffin 350888a09821a98ac0680fad765217302858e70fa4Paul Duffin /** 360888a09821a98ac0680fad765217302858e70fa4Paul Duffin * Returns the left child of the specified node, or {@link Optional#absent()} if the specified 370888a09821a98ac0680fad765217302858e70fa4Paul Duffin * node has no left child. 380888a09821a98ac0680fad765217302858e70fa4Paul Duffin */ 390888a09821a98ac0680fad765217302858e70fa4Paul Duffin public abstract Optional<T> leftChild(T root); 400888a09821a98ac0680fad765217302858e70fa4Paul Duffin 410888a09821a98ac0680fad765217302858e70fa4Paul Duffin /** 420888a09821a98ac0680fad765217302858e70fa4Paul Duffin * Returns the right child of the specified node, or {@link Optional#absent()} if the specified 430888a09821a98ac0680fad765217302858e70fa4Paul Duffin * node has no right child. 440888a09821a98ac0680fad765217302858e70fa4Paul Duffin */ 450888a09821a98ac0680fad765217302858e70fa4Paul Duffin public abstract Optional<T> rightChild(T root); 460888a09821a98ac0680fad765217302858e70fa4Paul Duffin 470888a09821a98ac0680fad765217302858e70fa4Paul Duffin /** 480888a09821a98ac0680fad765217302858e70fa4Paul Duffin * Returns the children of this node, in left-to-right order. 490888a09821a98ac0680fad765217302858e70fa4Paul Duffin */ 500888a09821a98ac0680fad765217302858e70fa4Paul Duffin @Override 510888a09821a98ac0680fad765217302858e70fa4Paul Duffin public final Iterable<T> children(final T root) { 520888a09821a98ac0680fad765217302858e70fa4Paul Duffin checkNotNull(root); 530888a09821a98ac0680fad765217302858e70fa4Paul Duffin return new FluentIterable<T>() { 540888a09821a98ac0680fad765217302858e70fa4Paul Duffin @Override 550888a09821a98ac0680fad765217302858e70fa4Paul Duffin public Iterator<T> iterator() { 560888a09821a98ac0680fad765217302858e70fa4Paul Duffin return new AbstractIterator<T>() { 570888a09821a98ac0680fad765217302858e70fa4Paul Duffin boolean doneLeft; 580888a09821a98ac0680fad765217302858e70fa4Paul Duffin boolean doneRight; 590888a09821a98ac0680fad765217302858e70fa4Paul Duffin 600888a09821a98ac0680fad765217302858e70fa4Paul Duffin @Override 610888a09821a98ac0680fad765217302858e70fa4Paul Duffin protected T computeNext() { 620888a09821a98ac0680fad765217302858e70fa4Paul Duffin if (!doneLeft) { 630888a09821a98ac0680fad765217302858e70fa4Paul Duffin doneLeft = true; 640888a09821a98ac0680fad765217302858e70fa4Paul Duffin Optional<T> left = leftChild(root); 650888a09821a98ac0680fad765217302858e70fa4Paul Duffin if (left.isPresent()) { 660888a09821a98ac0680fad765217302858e70fa4Paul Duffin return left.get(); 670888a09821a98ac0680fad765217302858e70fa4Paul Duffin } 680888a09821a98ac0680fad765217302858e70fa4Paul Duffin } 690888a09821a98ac0680fad765217302858e70fa4Paul Duffin if (!doneRight) { 700888a09821a98ac0680fad765217302858e70fa4Paul Duffin doneRight = true; 710888a09821a98ac0680fad765217302858e70fa4Paul Duffin Optional<T> right = rightChild(root); 720888a09821a98ac0680fad765217302858e70fa4Paul Duffin if (right.isPresent()) { 730888a09821a98ac0680fad765217302858e70fa4Paul Duffin return right.get(); 740888a09821a98ac0680fad765217302858e70fa4Paul Duffin } 750888a09821a98ac0680fad765217302858e70fa4Paul Duffin } 760888a09821a98ac0680fad765217302858e70fa4Paul Duffin return endOfData(); 770888a09821a98ac0680fad765217302858e70fa4Paul Duffin } 780888a09821a98ac0680fad765217302858e70fa4Paul Duffin }; 790888a09821a98ac0680fad765217302858e70fa4Paul Duffin } 800888a09821a98ac0680fad765217302858e70fa4Paul Duffin }; 810888a09821a98ac0680fad765217302858e70fa4Paul Duffin } 820888a09821a98ac0680fad765217302858e70fa4Paul Duffin 830888a09821a98ac0680fad765217302858e70fa4Paul Duffin // TODO(user): see if any significant optimizations are possible for breadthFirstIterator 840888a09821a98ac0680fad765217302858e70fa4Paul Duffin 850888a09821a98ac0680fad765217302858e70fa4Paul Duffin public final FluentIterable<T> inOrderTraversal(final T root) { 860888a09821a98ac0680fad765217302858e70fa4Paul Duffin checkNotNull(root); 870888a09821a98ac0680fad765217302858e70fa4Paul Duffin return new FluentIterable<T>() { 880888a09821a98ac0680fad765217302858e70fa4Paul Duffin @Override 890888a09821a98ac0680fad765217302858e70fa4Paul Duffin public UnmodifiableIterator<T> iterator() { 900888a09821a98ac0680fad765217302858e70fa4Paul Duffin return new InOrderIterator(root); 910888a09821a98ac0680fad765217302858e70fa4Paul Duffin } 920888a09821a98ac0680fad765217302858e70fa4Paul Duffin }; 930888a09821a98ac0680fad765217302858e70fa4Paul Duffin } 940888a09821a98ac0680fad765217302858e70fa4Paul Duffin 950888a09821a98ac0680fad765217302858e70fa4Paul Duffin private static final class InOrderNode<T> { 960888a09821a98ac0680fad765217302858e70fa4Paul Duffin final T node; 970888a09821a98ac0680fad765217302858e70fa4Paul Duffin boolean hasExpandedLeft; 980888a09821a98ac0680fad765217302858e70fa4Paul Duffin 990888a09821a98ac0680fad765217302858e70fa4Paul Duffin InOrderNode(T node) { 1000888a09821a98ac0680fad765217302858e70fa4Paul Duffin this.node = checkNotNull(node); 1010888a09821a98ac0680fad765217302858e70fa4Paul Duffin this.hasExpandedLeft = false; 1020888a09821a98ac0680fad765217302858e70fa4Paul Duffin } 1030888a09821a98ac0680fad765217302858e70fa4Paul Duffin } 1040888a09821a98ac0680fad765217302858e70fa4Paul Duffin 1050888a09821a98ac0680fad765217302858e70fa4Paul Duffin private final class InOrderIterator extends AbstractIterator<T> { 1060888a09821a98ac0680fad765217302858e70fa4Paul Duffin private final LinkedList<InOrderNode<T>> stack; 1070888a09821a98ac0680fad765217302858e70fa4Paul Duffin 1080888a09821a98ac0680fad765217302858e70fa4Paul Duffin InOrderIterator(T root) { 1090888a09821a98ac0680fad765217302858e70fa4Paul Duffin this.stack = Lists.newLinkedList(); 1100888a09821a98ac0680fad765217302858e70fa4Paul Duffin stack.addLast(new InOrderNode<T>(root)); 1110888a09821a98ac0680fad765217302858e70fa4Paul Duffin } 1120888a09821a98ac0680fad765217302858e70fa4Paul Duffin 1130888a09821a98ac0680fad765217302858e70fa4Paul Duffin @Override 1140888a09821a98ac0680fad765217302858e70fa4Paul Duffin protected T computeNext() { 1150888a09821a98ac0680fad765217302858e70fa4Paul Duffin while (!stack.isEmpty()) { 1160888a09821a98ac0680fad765217302858e70fa4Paul Duffin InOrderNode<T> inOrderNode = stack.getLast(); 1170888a09821a98ac0680fad765217302858e70fa4Paul Duffin if (inOrderNode.hasExpandedLeft) { 1180888a09821a98ac0680fad765217302858e70fa4Paul Duffin stack.removeLast(); 1190888a09821a98ac0680fad765217302858e70fa4Paul Duffin pushIfPresent(rightChild(inOrderNode.node)); 1200888a09821a98ac0680fad765217302858e70fa4Paul Duffin return inOrderNode.node; 1210888a09821a98ac0680fad765217302858e70fa4Paul Duffin } else { 1220888a09821a98ac0680fad765217302858e70fa4Paul Duffin inOrderNode.hasExpandedLeft = true; 1230888a09821a98ac0680fad765217302858e70fa4Paul Duffin pushIfPresent(leftChild(inOrderNode.node)); 1240888a09821a98ac0680fad765217302858e70fa4Paul Duffin } 1250888a09821a98ac0680fad765217302858e70fa4Paul Duffin } 1260888a09821a98ac0680fad765217302858e70fa4Paul Duffin return endOfData(); 1270888a09821a98ac0680fad765217302858e70fa4Paul Duffin } 1280888a09821a98ac0680fad765217302858e70fa4Paul Duffin 1290888a09821a98ac0680fad765217302858e70fa4Paul Duffin private void pushIfPresent(Optional<T> node) { 1300888a09821a98ac0680fad765217302858e70fa4Paul Duffin if (node.isPresent()) { 1310888a09821a98ac0680fad765217302858e70fa4Paul Duffin stack.addLast(new InOrderNode<T>(node.get())); 1320888a09821a98ac0680fad765217302858e70fa4Paul Duffin } 1330888a09821a98ac0680fad765217302858e70fa4Paul Duffin } 1340888a09821a98ac0680fad765217302858e70fa4Paul Duffin } 1350888a09821a98ac0680fad765217302858e70fa4Paul Duffin} 136