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