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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15 | package de.ugoe.cs.autoquest.usageprofiles;
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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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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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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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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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33 | * </p>
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34 | *
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35 | * @author Steffen Herbold, Patrick Harms
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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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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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49 |
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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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56 |
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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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63 |
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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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70 |
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71 | /**
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72 | * <p>
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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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76 | private SymbolComparator<T> comparator;
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77 |
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78 | /**
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79 | * <p>
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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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82 | * The comparator used by the tree node will be a {@link DefaultSymbolComparator}.
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83 | * </p>
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84 | */
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85 | TrieNode() {
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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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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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119 |
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120 | /**
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121 | * <p>
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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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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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129 | TrieNode(T symbol, SymbolComparator<T> comparator) {
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130 | if (symbol == null) {
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131 | throw new IllegalArgumentException
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132 | ("symbol must not be null. null is reserved for root node!");
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133 | }
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134 | this.symbol = symbol;
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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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141 | count = 0;
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142 | children = new LinkedList<TrieNode<T>>();
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143 | }
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144 |
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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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154 | throw new IllegalArgumentException("other must not be null");
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155 | }
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156 | symbol = other.symbol;
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157 | count = other.count;
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158 | comparator = other.comparator;
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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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164 |
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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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176 | if (!comparator.equals(symbol, subsequence.get(0))) { // should be guaranteed by
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177 | // the recursion/TrieRoot!
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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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188 |
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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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199 |
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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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210 |
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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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225 | node = new TrieNode<T>(symbol, comparator);
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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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230 |
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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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243 | if (comparator.equals(child.getSymbol(), symbol)) {
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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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249 |
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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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260 |
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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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286 |
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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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303 |
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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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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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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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327 |
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328 | /**
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329 | * <p>
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330 | * Generates a {@link Tree} representation of the trie.
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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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352 |
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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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380 |
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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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391 |
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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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402 |
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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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422 |
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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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443 |
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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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459 |
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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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463 | * {@link #children} are equal. For the comparison of their symbols the comparator is used.
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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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468 | @SuppressWarnings({ "rawtypes", "unchecked" })
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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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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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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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489 |
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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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506 | }
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