01 /*
02 * Java Genetic Algorithm Library (jenetics-5.2.0).
03 * Copyright (c) 2007-2020 Franz Wilhelmstötter
04 *
05 * Licensed under the Apache License, Version 2.0 (the "License");
06 * you may not use this file except in compliance with the License.
07 * You may obtain a copy of the License at
08 *
09 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 *
17 * Author:
18 * Franz Wilhelmstötter (franz.wilhelmstoetter@gmail.com)
19 */
20 package io.jenetics.ext.util;
21
22 import static java.util.Collections.singletonList;
23 import static java.util.Objects.requireNonNull;
24
25 import java.util.ArrayDeque;
26 import java.util.Deque;
27 import java.util.Iterator;
28 import java.util.NoSuchElementException;
29
30 /**
31 * Preorder iterator of the tree.
32 *
33 * @author <a href="mailto:franz.wilhelmstoetter@gmail.com">Franz Wilhelmstötter</a>
34 * @version 5.2
35 * @since 3.9
36 */
37 final class TreeNodePreorderIterator<V, T extends Tree<V, T>>
38 implements Iterator<T>
39 {
40 private final Deque<Iterator<T>> _deque = new ArrayDeque<>();
41
42 /**
43 * Create a new preorder iterator of the given tree {@code root}.
44 *
45 * @param root the root node of the tree
46 * @throws NullPointerException if the given {@code root} node is
47 * {@code null}
48 */
49 TreeNodePreorderIterator(final T root) {
50 requireNonNull(root);
51 _deque.push(singletonList(root).iterator());
52 }
53
54 @Override
55 public boolean hasNext() {
56 final Iterator<T> peek = _deque.peek();
57 return peek != null && peek.hasNext();
58 }
59
60 @Override
61 public T next() {
62 final Iterator<T> it = _deque.peek();
63 if (it == null) {
64 throw new NoSuchElementException("No next element.");
65 }
66
67 final T node = it.next();
68 if (!it.hasNext()) {
69 _deque.pop();
70 }
71
72 final Iterator<T> children = node.childIterator();
73 if (children.hasNext()) {
74 _deque.push(children);
75 }
76
77 return node;
78 }
79 }
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