1 | package de.ugoe.cs.eventbench.models;
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2 |
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3 | import java.io.Serializable;
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4 | import java.security.InvalidParameterException;
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5 | import java.util.Collection;
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6 | import java.util.LinkedList;
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7 | import java.util.List;
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8 | import java.util.Set;
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9 |
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10 | import de.ugoe.cs.eventbench.models.Trie.Edge;
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11 | import de.ugoe.cs.eventbench.models.Trie.TrieVertex;
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12 | import de.ugoe.cs.util.StringTools;
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13 | import edu.uci.ics.jung.graph.DelegateTree;
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14 | import edu.uci.ics.jung.graph.Tree;
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15 |
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16 | /**
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17 | * <p>
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18 | * This class implements a node of a trie. Each node is associated with a symbol
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19 | * and has a counter. The counter marks the number of occurences of the sequence
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20 | * defined by the path from the root of the trie to this node.
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21 | * </p>
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22 | *
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23 | * @author Steffen Herbold
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24 | *
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25 | * @param <T>
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26 | * Type of the symbols that are stored in the trie.
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27 | * @see Trie
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28 | */
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29 | class TrieNode<T> implements Serializable {
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30 |
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31 | /**
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32 | * <p>
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33 | * Id for object serialization.
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34 | * </p>
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35 | */
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36 | private static final long serialVersionUID = 1L;
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37 |
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38 | /**
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39 | * <p>
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40 | * Counter for the number of occurences of the sequence.
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41 | * </p>
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42 | */
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43 | private int count;
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44 |
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45 | /**
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46 | * <p>
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47 | * Symbol associated with the node.
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48 | * </p>
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49 | */
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50 | private final T symbol;
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51 |
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52 | /**
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53 | * <p>
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54 | * Child nodes of this node. If the node is a leaf this collection is empty.
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55 | * </p>
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56 | */
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57 | private Collection<TrieNode<T>> children;
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58 |
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59 | /**
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60 | * <p>
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61 | * Constructor. Creates a new TrieNode without a symbol associated.<br>
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62 | * <b>This constructor should only be used to create the root node of the
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63 | * trie!</b>
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64 | * </p>
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65 | */
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66 | TrieNode() {
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67 | this.symbol = null;
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68 | count = 0;
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69 | children = new LinkedList<TrieNode<T>>();
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70 | }
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71 |
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72 | /**
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73 | * <p>
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74 | * Constructor. Creates a new TrieNode. The symbol must not be null.
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75 | * </p>
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76 | *
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77 | * @param symbol
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78 | * symbol associated with the trie node
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79 | */
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80 | public TrieNode(T symbol) {
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81 | if (symbol == null) {
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82 | throw new InvalidParameterException(
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83 | "symbol must not be null. null is reserved for root node!");
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84 | }
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85 | this.symbol = symbol;
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86 | count = 0;
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87 | children = new LinkedList<TrieNode<T>>();
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88 | }
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89 |
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90 | /**
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91 | * <p>
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92 | * Adds a given subsequence to the trie and increases the counters
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93 | * accordingly.
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94 | * </p>
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95 | *
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96 | * @param subsequence
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97 | * subsequence whose counters are increased
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98 | * @see Trie#add(List)
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99 | */
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100 | public void add(List<T> subsequence) {
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101 | if (!subsequence.isEmpty()) {
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102 | if (!symbol.equals(subsequence.get(0))) { // should be guaranteed by
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103 | // the
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104 | // recursion/TrieRoot!
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105 | throw new AssertionError("Invalid trie operation!");
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106 | }
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107 | count++;
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108 | subsequence.remove(0);
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109 | if (!subsequence.isEmpty()) {
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110 | T nextSymbol = subsequence.get(0);
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111 | getChildCreate(nextSymbol).add(subsequence);
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112 | }
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113 | }
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114 | }
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115 |
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116 | /**
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117 | * <p>
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118 | * Returns the symbol associated with the node.
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119 | * </p>
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120 | *
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121 | * @return symbol associated with the node
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122 | */
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123 | public T getSymbol() {
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124 | return symbol;
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125 | }
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126 |
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127 | /**
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128 | * <p>
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129 | * Returns the number of occurences of the sequence represented by the node.
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130 | * </p>
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131 | *
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132 | * @return number of occurences of the sequence represented by the node
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133 | */
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134 | public int getCount() {
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135 | return count;
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136 | }
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137 |
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138 | /**
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139 | * <p>
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140 | * Returns the child of the node associated with the given symbol or creates
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141 | * it if it does not exist yet.
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142 | * </p>
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143 | *
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144 | * @param symbol
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145 | * symbol whose node is required
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146 | * @return node associated with the symbol
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147 | * @see Trie#getChildCreate(Object)
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148 | */
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149 | protected TrieNode<T> getChildCreate(T symbol) {
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150 | TrieNode<T> node = getChild(symbol);
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151 | if (node == null) {
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152 | node = new TrieNode<T>(symbol);
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153 | children.add(node);
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154 | }
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155 | return node;
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156 | }
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157 |
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158 | /**
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159 | * <p>
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160 | * Returns the child of the node associated with the given symbol or null if
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161 | * it does not exist.
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162 | * </p>
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163 | *
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164 | * @param symbol
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165 | * symbol whose node is required
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166 | * @return node associated with the symbol; null if no such node exists
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167 | * @see Trie#getChild(Object)
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168 | */
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169 | protected TrieNode<T> getChild(T symbol) {
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170 | for (TrieNode<T> child : children) {
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171 | if (child.getSymbol().equals(symbol)) {
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172 | return child;
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173 | }
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174 | }
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175 | return null;
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176 | }
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177 |
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178 | /**
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179 | * <p>
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180 | * Searches the sub-trie of this trie node for a given sequence and returns
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181 | * the node associated with the sequence or null if no such node is found.
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182 | * </p>
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183 | *
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184 | * @param sequence
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185 | * sequence that is searched for
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186 | * @return node associated with the sequence
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187 | * @see Trie#find(List)
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188 | */
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189 | public TrieNode<T> find(List<T> subsequence) {
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190 | TrieNode<T> result = null;
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191 | if (subsequence.isEmpty()) {
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192 | result = this;
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193 | } else {
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194 | TrieNode<T> node = getChild(subsequence.get(0));
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195 | if (node != null) {
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196 | subsequence.remove(0);
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197 | result = node.find(subsequence);
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198 | }
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199 | }
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200 | return result;
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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 | * Returns a collection of all symbols that follow a this node, i.e., the
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206 | * symbols associated with the children of this node.
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207 | * </p>
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208 | *
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209 | * @return symbols follow this node
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210 | * @see TrieNode#getFollowingSymbols()
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211 | */
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212 | public Collection<T> getFollowingSymbols() {
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213 | Collection<T> followingSymbols = new LinkedList<T>();
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214 | for (TrieNode<T> child : children) {
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215 | followingSymbols.add(child.getSymbol());
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216 | }
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217 | return followingSymbols;
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218 | }
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219 |
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220 | /**
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221 | * <p>
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222 | * The string representation of a node is {@code symbol.toString()#count}
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223 | * </p>
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224 | *
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225 | * @see java.lang.Object#toString()
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226 | */
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227 | @Override
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228 | public String toString() {
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229 | String str = symbol.toString() + " #" + count;
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230 | if (!children.isEmpty()) {
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231 | str += StringTools.ENDLINE + children.toString();
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232 | }
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233 | return str;
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234 | }
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235 |
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236 | /**
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237 | * <p>
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238 | * Generates a {@link Tree} represenation of the trie.
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239 | * </p>
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240 | *
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241 | * @param parent
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242 | * parent vertex in the generated tree
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243 | * @param graph
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244 | * complete tree
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245 | */
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246 | void getGraph(TrieVertex parent, DelegateTree<TrieVertex, Edge> graph) {
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247 | TrieVertex currentVertex;
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248 | if (symbol == null) {
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249 | currentVertex = new TrieVertex("root");
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250 | graph.addVertex(currentVertex);
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251 | } else {
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252 | currentVertex = new TrieVertex(getSymbol().toString() + "#"
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253 | + getCount());
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254 | graph.addChild(new Edge(), parent, currentVertex);
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255 | }
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256 | for (TrieNode<T> node : children) {
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257 | node.getGraph(currentVertex, graph);
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258 | }
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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 | * Appends the current node to the dot representation of the trie.
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264 | * </p>
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265 | *
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266 | * @param stringBuilder
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267 | * {@link StringBuilder} to which the dot representation is
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268 | * appended
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269 | */
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270 | void appendDotRepresentation(StringBuilder stringBuilder) {
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271 | String thisSaneId;
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272 | if (symbol == null) {
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273 | thisSaneId = "root";
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274 | } else {
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275 | thisSaneId = symbol.toString().replace("\"", "\\\"")
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276 | .replaceAll("[\r\n]", "")
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277 | + "#" + count;
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278 | }
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279 | stringBuilder.append(" " + hashCode() + " [label=\"" + thisSaneId
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280 | + "\"];" + StringTools.ENDLINE);
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281 | for (TrieNode<T> childNode : children) {
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282 | stringBuilder.append(" " + hashCode() + " -> "
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283 | + childNode.hashCode() + ";" + StringTools.ENDLINE);
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284 | }
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285 | for (TrieNode<T> childNode : children) {
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286 | childNode.appendDotRepresentation(stringBuilder);
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287 | }
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288 | }
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289 |
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290 | /**
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291 | * <p>
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292 | * Checks if the node is a leaf.
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293 | * </p>
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294 | *
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295 | * @return true if the node is a leaf, false otherwise.
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296 | */
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297 | protected boolean isLeaf() {
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298 | return children.isEmpty();
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299 | }
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300 |
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301 | /**
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302 | * <p>
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303 | * Recursive methods that collects all nodes that are ancestors of leafs and
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304 | * stores them in the set.
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305 | * </p>
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306 | *
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307 | * @param ancestors
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308 | * set of all ancestors of leafs
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309 | */
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310 | protected void getLeafAncestors(Set<TrieNode<T>> ancestors) {
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311 | boolean isAncestor = false;
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312 | for (TrieNode<T> child : children) {
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313 | child.getLeafAncestors(ancestors);
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314 | isAncestor |= child.isLeaf();
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315 | }
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316 | if (isAncestor) {
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317 | ancestors.add(this);
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318 | }
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319 | }
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320 |
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321 | /**
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322 | * <p>Returns the number of descendants of this node that are leafs. This does not only include direct children of this node, but all leafs in the sub-trie with this node as root.
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323 | * </p>
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324 | * @return
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325 | */
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326 | protected int getNumLeafs() {
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327 | int numLeafs = 0;
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328 | for( TrieNode<T> child : children) {
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329 | if( child.isLeaf() ) {
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330 | numLeafs++;
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331 | } else {
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332 | numLeafs += child.getNumLeafs();
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333 | }
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334 | }
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335 | return numLeafs;
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336 | }
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337 | }
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