[927] | 1 | // Copyright 2012 Georg-August-Universität Göttingen, Germany
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| 2 | //
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| 3 | // Licensed under the Apache License, Version 2.0 (the "License");
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| 4 | // you may not use this file except in compliance with the License.
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| 5 | // You may obtain a copy of the License at
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| 6 | //
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| 7 | // http://www.apache.org/licenses/LICENSE-2.0
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| 8 | //
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| 9 | // Unless required by applicable law or agreed to in writing, software
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| 10 | // distributed under the License is distributed on an "AS IS" BASIS,
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| 11 | // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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| 12 | // See the License for the specific language governing permissions and
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| 13 | // limitations under the License.
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| 14 |
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[922] | 15 | package de.ugoe.cs.autoquest.usageprofiles;
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[518] | 16 |
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| 17 | import java.io.Serializable;
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| 18 | import java.util.Collection;
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| 19 | import java.util.LinkedList;
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| 20 | import java.util.List;
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| 21 |
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[922] | 22 | import de.ugoe.cs.autoquest.usageprofiles.Trie.Edge;
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| 23 | import de.ugoe.cs.autoquest.usageprofiles.Trie.TrieVertex;
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[518] | 24 | import de.ugoe.cs.util.StringTools;
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| 25 | import edu.uci.ics.jung.graph.DelegateTree;
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| 26 | import edu.uci.ics.jung.graph.Tree;
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| 27 |
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| 28 | /**
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| 29 | * <p>
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[559] | 30 | * This class implements a node of a trie. Each node is associated with a symbol and has a counter.
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| 31 | * The counter marks the number of occurences of the sequence defined by the path from the root of
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| 32 | * the trie to this node.
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[518] | 33 | * </p>
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| 34 | *
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[1060] | 35 | * @author Steffen Herbold, Patrick Harms
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[518] | 36 | *
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| 37 | * @param <T>
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| 38 | * Type of the symbols that are stored in the trie.
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| 39 | * @see Trie
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| 40 | */
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| 41 | class TrieNode<T> implements Serializable {
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| 42 |
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[559] | 43 | /**
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| 44 | * <p>
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| 45 | * Id for object serialization.
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| 46 | * </p>
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| 47 | */
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| 48 | private static final long serialVersionUID = 1L;
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[518] | 49 |
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[559] | 50 | /**
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| 51 | * <p>
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| 52 | * Counter for the number of occurences of the sequence.
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| 53 | * </p>
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| 54 | */
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| 55 | private int count;
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[518] | 56 |
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[559] | 57 | /**
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| 58 | * <p>
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| 59 | * Symbol associated with the node.
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| 60 | * </p>
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| 61 | */
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| 62 | private final T symbol;
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[518] | 63 |
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[559] | 64 | /**
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| 65 | * <p>
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| 66 | * Child nodes of this node. If the node is a leaf this collection is empty.
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| 67 | * </p>
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| 68 | */
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| 69 | private Collection<TrieNode<T>> children;
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[518] | 70 |
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[559] | 71 | /**
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| 72 | * <p>
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[1060] | 73 | * Comparator to be used for comparing the symbols with each other
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| 74 | * </p>
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| 75 | */
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[1189] | 76 | private SymbolComparator<T> comparator;
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[1060] | 77 |
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| 78 | /**
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| 79 | * <p>
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[559] | 80 | * Constructor. Creates a new TrieNode without a symbol associated.<br>
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| 81 | * <b>This constructor should only be used to create the root node of the trie!</b>
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[1060] | 82 | * The comparator used by the tree node will be a {@link DefaultSymbolComparator}.
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[559] | 83 | * </p>
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| 84 | */
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| 85 | TrieNode() {
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[1060] | 86 | this(new DefaultSymbolComparator<T>());
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| 87 | }
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| 88 |
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| 89 | /**
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| 90 | * <p>
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| 91 | * Constructor. Creates a new TrieNode. The symbol must not be null.
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| 92 | * The comparator used by the tree node will be a {@link DefaultSymbolComparator}.
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| 93 | * </p>
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| 94 | *
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| 95 | * @param symbol
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| 96 | * symbol associated with the trie node
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| 97 | */
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| 98 | TrieNode(T symbol) {
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| 99 | this(symbol, new DefaultSymbolComparator<T>());
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| 100 | }
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| 101 |
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| 102 | /**
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| 103 | * <p>
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| 104 | * Constructor. Creates a new TrieNode without a symbol associated using the provided
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| 105 | * comparator.<br>
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| 106 | * <b>This constructor should only be used to create the root node of the trie!</b>
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| 107 | * <br>The comparator must not be null.
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| 108 | * </p>
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| 109 | */
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| 110 | TrieNode(SymbolComparator<T> comparator) {
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| 111 | if (comparator == null) {
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| 112 | throw new IllegalArgumentException("comparator must not be null!");
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| 113 | }
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| 114 | this.comparator = comparator;
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[559] | 115 | this.symbol = null;
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| 116 | count = 0;
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| 117 | children = new LinkedList<TrieNode<T>>();
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| 118 | }
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[518] | 119 |
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[559] | 120 | /**
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| 121 | * <p>
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[1060] | 122 | * Constructor. Creates a new TrieNode using the provided comparator. The symbol and the
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| 123 | * comparator must not be null.
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[559] | 124 | * </p>
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| 125 | *
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| 126 | * @param symbol
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| 127 | * symbol associated with the trie node
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| 128 | */
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[1060] | 129 | TrieNode(T symbol, SymbolComparator<T> comparator) {
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[559] | 130 | if (symbol == null) {
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[1060] | 131 | throw new IllegalArgumentException
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| 132 | ("symbol must not be null. null is reserved for root node!");
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[559] | 133 | }
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| 134 | this.symbol = symbol;
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[1060] | 135 |
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| 136 | if (comparator == null) {
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| 137 | throw new IllegalArgumentException("comparator must not be null!");
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| 138 | }
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| 139 | this.comparator = comparator;
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| 140 |
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[559] | 141 | count = 0;
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| 142 | children = new LinkedList<TrieNode<T>>();
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| 143 | }
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[518] | 144 |
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[559] | 145 | /**
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| 146 | * <p>
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| 147 | * Copy-Constructor. Creates a new TrieNode as copy of other. Other must not be null.
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| 148 | * </p>
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| 149 | *
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| 150 | * @param other
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| 151 | */
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| 152 | TrieNode(TrieNode<T> other) {
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| 153 | if (other == null) {
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[766] | 154 | throw new IllegalArgumentException("other must not be null");
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[559] | 155 | }
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| 156 | symbol = other.symbol;
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| 157 | count = other.count;
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[1060] | 158 | comparator = other.comparator;
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[559] | 159 | children = new LinkedList<TrieNode<T>>();
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| 160 | for (TrieNode<T> child : other.children) {
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| 161 | children.add(new TrieNode<T>(child));
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| 162 | }
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| 163 | }
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[518] | 164 |
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[559] | 165 | /**
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| 166 | * <p>
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| 167 | * Adds a given subsequence to the trie and increases the counters accordingly.
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| 168 | * </p>
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| 169 | *
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| 170 | * @param subsequence
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| 171 | * subsequence whose counters are increased
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| 172 | * @see Trie#add(List)
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| 173 | */
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| 174 | public void add(List<T> subsequence) {
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| 175 | if (!subsequence.isEmpty()) {
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[1060] | 176 | if (!comparator.equals(symbol, subsequence.get(0))) { // should be guaranteed by
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| 177 | // the recursion/TrieRoot!
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[559] | 178 | throw new AssertionError("Invalid trie operation!");
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| 179 | }
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| 180 | count++;
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| 181 | subsequence.remove(0);
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| 182 | if (!subsequence.isEmpty()) {
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| 183 | T nextSymbol = subsequence.get(0);
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| 184 | getChildCreate(nextSymbol).add(subsequence);
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| 185 | }
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| 186 | }
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| 187 | }
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[518] | 188 |
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[559] | 189 | /**
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| 190 | * <p>
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| 191 | * Returns the symbol associated with the node.
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| 192 | * </p>
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| 193 | *
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| 194 | * @return symbol associated with the node
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| 195 | */
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| 196 | public T getSymbol() {
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| 197 | return symbol;
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| 198 | }
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[518] | 199 |
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[559] | 200 | /**
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| 201 | * <p>
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| 202 | * Returns the number of occurences of the sequence represented by the node.
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| 203 | * </p>
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| 204 | *
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| 205 | * @return number of occurences of the sequence represented by the node
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| 206 | */
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| 207 | public int getCount() {
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| 208 | return count;
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| 209 | }
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[518] | 210 |
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[559] | 211 | /**
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| 212 | * <p>
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| 213 | * Returns the child of the node associated with the given symbol or creates it if it does not
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| 214 | * exist yet.
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| 215 | * </p>
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| 216 | *
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| 217 | * @param symbol
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| 218 | * symbol whose node is required
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| 219 | * @return node associated with the symbol
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| 220 | * @see Trie#getChildCreate(Object)
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| 221 | */
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| 222 | protected TrieNode<T> getChildCreate(T symbol) {
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| 223 | TrieNode<T> node = getChild(symbol);
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| 224 | if (node == null) {
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[1060] | 225 | node = new TrieNode<T>(symbol, comparator);
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[559] | 226 | children.add(node);
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| 227 | }
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| 228 | return node;
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| 229 | }
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[518] | 230 |
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[559] | 231 | /**
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| 232 | * <p>
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| 233 | * Returns the child of the node associated with the given symbol or null if it does not exist.
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| 234 | * </p>
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| 235 | *
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| 236 | * @param symbol
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| 237 | * symbol whose node is required
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| 238 | * @return node associated with the symbol; null if no such node exists
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| 239 | * @see Trie#getChild(Object)
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| 240 | */
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| 241 | protected TrieNode<T> getChild(T symbol) {
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| 242 | for (TrieNode<T> child : children) {
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[1060] | 243 | if (comparator.equals(child.getSymbol(), symbol)) {
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[559] | 244 | return child;
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| 245 | }
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| 246 | }
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| 247 | return null;
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| 248 | }
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[518] | 249 |
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[559] | 250 | /**
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| 251 | * <p>
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| 252 | * Returns all children of this node.
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| 253 | * </p>
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| 254 | *
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| 255 | * @return children of this node
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| 256 | */
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| 257 | protected Collection<TrieNode<T>> getChildren() {
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| 258 | return children;
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| 259 | }
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[518] | 260 |
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[559] | 261 | /**
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| 262 | * <p>
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| 263 | * Searches the sub-trie of this trie node for a given sequence and returns the node associated
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| 264 | * with the sequence or null if no such node is found.
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| 265 | * </p>
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| 266 | *
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| 267 | * @param sequence
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| 268 | * sequence that is searched for
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| 269 | * @return node associated with the sequence
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| 270 | * @see Trie#find(List)
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| 271 | */
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| 272 | public TrieNode<T> find(List<T> subsequence) {
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| 273 | TrieNode<T> result = null;
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| 274 | if (subsequence.isEmpty()) {
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| 275 | result = this;
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| 276 | }
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| 277 | else {
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| 278 | TrieNode<T> node = getChild(subsequence.get(0));
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| 279 | if (node != null) {
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| 280 | subsequence.remove(0);
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| 281 | result = node.find(subsequence);
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| 282 | }
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| 283 | }
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| 284 | return result;
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| 285 | }
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[518] | 286 |
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[559] | 287 | /**
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| 288 | * <p>
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| 289 | * Returns a collection of all symbols that follow a this node, i.e., the symbols associated
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| 290 | * with the children of this node.
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| 291 | * </p>
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| 292 | *
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| 293 | * @return symbols follow this node
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| 294 | * @see TrieNode#getFollowingSymbols()
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| 295 | */
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| 296 | public Collection<T> getFollowingSymbols() {
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| 297 | Collection<T> followingSymbols = new LinkedList<T>();
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| 298 | for (TrieNode<T> child : children) {
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| 299 | followingSymbols.add(child.getSymbol());
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| 300 | }
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| 301 | return followingSymbols;
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| 302 | }
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[518] | 303 |
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[559] | 304 | /**
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| 305 | * <p>
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| 306 | * The string representation of a node is {@code symbol.toString()#count}
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| 307 | * </p>
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| 308 | *
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| 309 | * @see java.lang.Object#toString()
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| 310 | */
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| 311 | @Override
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| 312 | public String toString() {
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[1060] | 313 | String str;
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| 314 |
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| 315 | if (symbol == null) {
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| 316 | str = "ROOT";
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| 317 | }
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| 318 | else {
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| 319 | str = symbol.toString() + " #" + count;
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| 320 | }
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| 321 |
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[559] | 322 | if (!children.isEmpty()) {
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| 323 | str += StringTools.ENDLINE + children.toString();
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| 324 | }
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| 325 | return str;
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| 326 | }
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[518] | 327 |
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[559] | 328 | /**
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| 329 | * <p>
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[1060] | 330 | * Generates a {@link Tree} representation of the trie.
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[559] | 331 | * </p>
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| 332 | *
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| 333 | * @param parent
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| 334 | * parent vertex in the generated tree
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| 335 | * @param graph
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| 336 | * complete tree
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| 337 | */
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| 338 | void getGraph(TrieVertex parent, DelegateTree<TrieVertex, Edge> graph) {
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| 339 | TrieVertex currentVertex;
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| 340 | if (isRoot()) {
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| 341 | currentVertex = new TrieVertex("root");
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| 342 | graph.addVertex(currentVertex);
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| 343 | }
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| 344 | else {
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| 345 | currentVertex = new TrieVertex(getSymbol().toString() + "#" + getCount());
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| 346 | graph.addChild(new Edge(), parent, currentVertex);
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| 347 | }
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| 348 | for (TrieNode<T> node : children) {
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| 349 | node.getGraph(currentVertex, graph);
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| 350 | }
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| 351 | }
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[518] | 352 |
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[559] | 353 | /**
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| 354 | * <p>
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| 355 | * Appends the current node to the dot representation of the trie.
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| 356 | * </p>
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| 357 | *
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| 358 | * @param stringBuilder
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| 359 | * {@link StringBuilder} to which the dot representation is appended
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| 360 | */
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| 361 | void appendDotRepresentation(StringBuilder stringBuilder) {
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| 362 | String thisSaneId;
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| 363 | if (isRoot()) {
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| 364 | thisSaneId = "root";
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| 365 | }
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| 366 | else {
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| 367 | thisSaneId =
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| 368 | symbol.toString().replace("\"", "\\\"").replaceAll("[\r\n]", "") + "#" + count;
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| 369 | }
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| 370 | stringBuilder.append(" " + hashCode() + " [label=\"" + thisSaneId + "\"];" +
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| 371 | StringTools.ENDLINE);
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| 372 | for (TrieNode<T> childNode : children) {
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| 373 | stringBuilder.append(" " + hashCode() + " -> " + childNode.hashCode() + ";" +
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| 374 | StringTools.ENDLINE);
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| 375 | }
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| 376 | for (TrieNode<T> childNode : children) {
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| 377 | childNode.appendDotRepresentation(stringBuilder);
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| 378 | }
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| 379 | }
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[518] | 380 |
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[559] | 381 | /**
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| 382 | * <p>
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| 383 | * Checks if the node is a leaf.
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| 384 | * </p>
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| 385 | *
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| 386 | * @return true if the node is a leaf, false otherwise.
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| 387 | */
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| 388 | protected boolean isLeaf() {
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| 389 | return children.isEmpty();
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| 390 | }
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[518] | 391 |
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[559] | 392 | /**
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| 393 | * <p>
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| 394 | * Checks if the node is the root.
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| 395 | * </p>
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| 396 | *
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| 397 | * @return true if the node is the root of the trie, false otherwise
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| 398 | */
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| 399 | protected boolean isRoot() {
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| 400 | return symbol == null;
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| 401 | }
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[518] | 402 |
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[559] | 403 | /**
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| 404 | * <p>
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| 405 | * Recursive methods that collects all nodes that are ancestors of leafs and stores them in the
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| 406 | * set.
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| 407 | * </p>
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| 408 | *
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| 409 | * @param ancestors
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| 410 | * set of all ancestors of leafs
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| 411 | */
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| 412 | protected void getLeafAncestors(List<TrieNode<T>> ancestors) {
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| 413 | boolean isAncestor = false;
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| 414 | for (TrieNode<T> child : children) {
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| 415 | child.getLeafAncestors(ancestors);
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| 416 | isAncestor |= child.isLeaf();
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| 417 | }
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| 418 | if (isAncestor) {
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| 419 | ancestors.add(this);
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| 420 | }
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| 421 | }
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[518] | 422 |
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[559] | 423 | /**
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| 424 | * <p>
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| 425 | * Returns the number of descendants of this node that are leafs. This does not only include
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| 426 | * direct children of this node, but all leafs in the sub-trie with this node as root.
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| 427 | * </p>
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| 428 | *
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| 429 | * @return number of leafs in this sub-trie
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| 430 | */
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| 431 | protected int getNumLeafs() {
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| 432 | int numLeafs = 0;
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| 433 | for (TrieNode<T> child : children) {
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| 434 | if (child.isLeaf()) {
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| 435 | numLeafs++;
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| 436 | }
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| 437 | else {
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| 438 | numLeafs += child.getNumLeafs();
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| 439 | }
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| 440 | }
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| 441 | return numLeafs;
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| 442 | }
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[518] | 443 |
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[559] | 444 | /**
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| 445 | * <p>
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| 446 | * Sets the {@link #count} of this node.
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| 447 | * </p>
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| 448 | * <p>
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| 449 | * This function should only be used sparingly and very carefully! The count is usually
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| 450 | * maintained automatically by the training procedures.
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| 451 | * </p>
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| 452 | *
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| 453 | * @param count
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| 454 | * new count
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| 455 | */
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| 456 | protected void setCount(int count) {
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| 457 | this.count = count;
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| 458 | }
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[518] | 459 |
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[559] | 460 | /**
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| 461 | * <p>
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| 462 | * Two TrieNodes are defined as equal, if their {@link #count}, {@link #symbol}, and
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[1060] | 463 | * {@link #children} are equal. For the comparison of their symbols the comparator is used.
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[559] | 464 | * </p>
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| 465 | *
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| 466 | * @see java.lang.Object#equals(java.lang.Object)
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| 467 | */
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[1060] | 468 | @SuppressWarnings({ "rawtypes", "unchecked" })
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[559] | 469 | @Override
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| 470 | public boolean equals(Object other) {
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| 471 | if (other == this) {
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| 472 | return true;
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| 473 | }
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| 474 | if (other instanceof TrieNode) {
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| 475 | TrieNode otherNode = (TrieNode) other;
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| 476 | if (symbol == null) {
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| 477 | return count == otherNode.count && otherNode.symbol == null &&
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| 478 | children.equals(otherNode.children);
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| 479 | }
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| 480 | else {
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[1060] | 481 | return count == otherNode.count &&
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| 482 | symbol.getClass().isInstance(((TrieNode) other).symbol) &&
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| 483 | comparator.equals(symbol, ((TrieNode<T>) other).symbol) &&
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[559] | 484 | children.equals(((TrieNode) other).children);
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| 485 | }
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| 486 | }
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| 487 | return false;
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| 488 | }
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[518] | 489 |
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[559] | 490 | /*
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| 491 | * (non-Javadoc)
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| 492 | *
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| 493 | * @see java.lang.Object#hashCode()
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| 494 | */
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| 495 | @Override
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| 496 | public int hashCode() {
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| 497 | int multiplier = 17;
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| 498 | int hash = 42;
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| 499 | if (symbol != null) {
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| 500 | hash = multiplier * hash + symbol.hashCode();
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| 501 | }
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| 502 | hash = multiplier * hash + count;
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| 503 | hash = multiplier * hash + children.hashCode();
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| 504 | return hash;
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| 505 | }
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[518] | 506 | }
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