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.LinkedHashSet;
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20 | import java.util.LinkedList;
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21 | import java.util.List;
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22 |
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23 | import de.ugoe.cs.util.StringTools;
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24 |
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25 | import edu.uci.ics.jung.graph.DelegateTree;
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26 | import edu.uci.ics.jung.graph.Graph;
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27 | import edu.uci.ics.jung.graph.Tree;
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28 |
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29 | /**
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30 | * <p>
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31 | * This class implements a <it>trie</it>, i.e., a tree of sequences that represents the occurrence
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32 | * of subsequences up to a predefined length. This length is the trie order.
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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 | *
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40 | * @see TrieNode
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41 | */
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42 | public class Trie<T> implements IDotCompatible, Serializable {
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43 |
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44 | /**
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45 | * <p>
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46 | * Id for object serialization.
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47 | * </p>
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48 | */
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49 | private static final long serialVersionUID = 1L;
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50 |
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51 | /**
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52 | * <p>
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53 | * Collection of all symbols occurring in the trie.
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54 | * </p>
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55 | */
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56 | private SymbolMap<T, T> knownSymbols;
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57 |
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58 | /**
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59 | * <p>
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60 | * Reference to the root of the trie.
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61 | * </p>
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62 | */
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63 | private final TrieNode<T> rootNode;
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64 |
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65 | /**
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66 | * <p>
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67 | * Strategy for handling symbols, i.e., for comparing and storing them
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68 | * </p>
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69 | */
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70 | private SymbolStrategy<T> strategy;
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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 trie with a {@link DefaultSymbolStrategy}.
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75 | * </p>
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76 | */
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77 | public Trie() {
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78 | this(new DefaultSymbolStrategy<T>());
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79 | }
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80 |
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81 | /**
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82 | * <p>
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83 | * Constructor. Creates a new trie that uses a specific {@link SymbolStrategy}.
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84 | * </p>
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85 | *
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86 | * @param strategy
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87 | * strategy to be used for managing symbols
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88 | *
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89 | * @throws IllegalArgumentException
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90 | * if the strategy is null
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91 | */
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92 | public Trie(SymbolStrategy<T> strategy) {
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93 | if (strategy == null) {
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94 | throw new IllegalArgumentException("strategy must not be null");
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95 | }
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96 | this.strategy = strategy;
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97 | rootNode = new TrieNode<T>(strategy);
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98 | knownSymbols = strategy.createSymbolMap();
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99 | }
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100 |
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101 | /**
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102 | * <p>
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103 | * Copy-Constructor. Creates a new trie as the copy of other. The other trie must not be null.
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104 | * </p>
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105 | *
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106 | * @param other
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107 | * trie that is copied
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108 | *
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109 | * @throws IllegalArgumentException
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110 | * if the other trie is null
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111 | */
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112 | public Trie(Trie<T> other) {
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113 | if (other == null) {
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114 | throw new IllegalArgumentException("other trie must not be null");
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115 | }
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116 | rootNode = new TrieNode<T>(other.rootNode);
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117 | strategy = other.strategy;
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118 | knownSymbols = strategy.copySymbolMap(other.knownSymbols);
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119 | }
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120 |
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121 | /**
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122 | * <p>
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123 | * Returns a collection of all symbols occurring in the trie.
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124 | * </p>
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125 | *
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126 | * @return symbols occurring in the trie
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127 | */
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128 | public Collection<T> getKnownSymbols() {
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129 | return new LinkedHashSet<T>(knownSymbols.getSymbols());
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130 | }
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131 |
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132 | /**
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133 | * <p>
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134 | * Trains the current trie using the given sequence and adds all subsequences of length
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135 | * {@code maxOrder}.
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136 | * </p>
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137 | *
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138 | * @param sequence
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139 | * sequence whose subsequences are added to the trie
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140 | * @param maxOrder
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141 | * maximum length of the subsequences added to the trie
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142 | */
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143 | public void train(List<T> sequence, int maxOrder) {
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144 | if (maxOrder < 1) {
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145 | return;
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146 | }
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147 | IncompleteMemory<T> latestActions = new IncompleteMemory<T>(maxOrder);
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148 | int i = 0;
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149 | for (T currentEvent : sequence) {
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150 | latestActions.add(currentEvent);
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151 | addToKnownSymbols(currentEvent);
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152 | i++;
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153 | if (i >= maxOrder) {
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154 | add(latestActions.getLast(maxOrder));
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155 | }
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156 | }
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157 | int sequenceLength = sequence.size();
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158 | int startIndex = Math.max(0, sequenceLength - maxOrder + 1);
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159 | for (int j = startIndex; j < sequenceLength; j++) {
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160 | add(sequence.subList(j, sequenceLength));
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161 | }
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162 | }
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163 |
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164 | /**
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165 | * <p>
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166 | * Adds a given subsequence to the trie and increases the counters accordingly. NOTE: This
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167 | * method does not add the symbols to the list of known symbols. This is only ensured using
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168 | * the method {@link #train(List, int)}.
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169 | * </p>
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170 | *
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171 | * @param subsequence
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172 | * subsequence whose counters are increased
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173 | * @see TrieNode#add(List)
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174 | */
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175 | protected void add(List<T> subsequence) {
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176 | if (subsequence != null && !subsequence.isEmpty()) {
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177 | subsequence = new LinkedList<T>(subsequence); // defensive copy!
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178 | T firstSymbol = subsequence.get(0);
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179 | TrieNode<T> node = getChildCreate(firstSymbol);
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180 | node.add(subsequence);
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181 | }
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182 | }
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183 |
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184 | /**
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185 | * <p>
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186 | * Returns the child of the root node associated with the given symbol or creates it if it does
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187 | * not exist yet.
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188 | * </p>
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189 | *
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190 | * @param symbol
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191 | * symbol whose node is required
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192 | * @return node associated with the symbol
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193 | * @see TrieNode#getChildCreate(Object)
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194 | */
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195 | protected TrieNode<T> getChildCreate(T symbol) {
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196 | return rootNode.getChildCreate(symbol);
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197 | }
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198 |
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199 | /**
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200 | * <p>
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201 | * Returns the child of the root node associated with the given symbol or null if it does not
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202 | * exist.
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203 | * </p>
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204 | *
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205 | * @param symbol
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206 | * symbol whose node is required
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207 | * @return node associated with the symbol; null if no such node exists
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208 | * @see TrieNode#getChild(Object)
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209 | */
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210 | protected TrieNode<T> getChild(T symbol) {
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211 | return rootNode.getChild(symbol);
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212 | }
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213 |
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214 | /**
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215 | * <p>
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216 | * Returns the number of occurrences of the given sequence.
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217 | * </p>
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218 | *
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219 | * @param sequence
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220 | * sequence whose number of occurrences is required
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221 | * @return number of occurrences of the sequence
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222 | */
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223 | public int getCount(List<T> sequence) {
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224 | int count = 0;
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225 | TrieNode<T> node = find(sequence);
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226 | if (node != null) {
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227 | count = node.getCount();
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228 | }
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229 | return count;
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230 | }
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231 |
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232 | /**
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233 | * <p>
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234 | * Returns the number of occurrences of the given prefix and a symbol that follows it.<br>
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235 | * Convenience function to simplify usage of {@link #getCount(List)}.
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236 | * </p>
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237 | *
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238 | * @param sequence
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239 | * prefix of the sequence
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240 | * @param follower
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241 | * suffix of the sequence
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242 | * @return number of occurrences of the sequence
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243 | * @see #getCount(List)
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244 | */
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245 | public int getCount(List<T> sequence, T follower) {
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246 | List<T> tmpSequence = new LinkedList<T>(sequence);
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247 | tmpSequence.add(follower);
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248 | return getCount(tmpSequence);
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249 |
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250 | }
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251 |
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252 | /**
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253 | * <p>
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254 | * Searches the trie for a given sequence and returns the node associated with the sequence or
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255 | * null if no such node is found.
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256 | * </p>
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257 | *
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258 | * @param sequence
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259 | * sequence that is searched for
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260 | * @return node associated with the sequence
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261 | * @see TrieNode#find(List)
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262 | */
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263 | public TrieNode<T> find(List<T> sequence) {
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264 | if (sequence == null || sequence.isEmpty()) {
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265 | return rootNode;
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266 | }
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267 | List<T> sequenceCopy = new LinkedList<T>(sequence);
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268 | TrieNode<T> result = null;
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269 | TrieNode<T> node = getChild(sequenceCopy.get(0));
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270 | if (node != null) {
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271 | sequenceCopy.remove(0);
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272 | result = node.find(sequenceCopy);
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273 | }
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274 | return result;
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275 | }
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276 |
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277 | /**
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278 | * <p>
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279 | * Returns a collection of all symbols that follow a given sequence in the trie. In case the
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280 | * sequence is not found or no symbols follow the sequence the result will be empty.
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281 | * </p>
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282 | *
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283 | * @param sequence
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284 | * sequence whose followers are returned
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285 | * @return symbols following the given sequence
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286 | * @see TrieNode#getFollowingSymbols()
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287 | */
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288 | public Collection<T> getFollowingSymbols(List<T> sequence) {
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289 | Collection<T> result = new LinkedList<T>();
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290 | TrieNode<T> node = find(sequence);
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291 | if (node != null) {
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292 | result = node.getFollowingSymbols();
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293 | }
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294 | return result;
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295 | }
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296 |
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297 | /**
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298 | * <p>
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299 | * Returns the longest suffix of the given context that is contained in the tree and whose
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300 | * children are leaves.
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301 | * </p>
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302 | *
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303 | * @param context
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304 | * context whose suffix is searched for
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305 | * @return longest suffix of the context
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306 | */
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307 | public List<T> getContextSuffix(List<T> context) {
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308 | List<T> contextSuffix;
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309 | if (context != null) {
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310 | contextSuffix = new LinkedList<T>(context); // defensive copy
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311 | }
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312 | else {
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313 | contextSuffix = new LinkedList<T>();
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314 | }
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315 | boolean suffixFound = false;
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316 |
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317 | while (!suffixFound) {
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318 | if (contextSuffix.isEmpty()) {
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319 | suffixFound = true; // suffix is the empty word
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320 | }
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321 | else {
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322 | TrieNode<T> node = find(contextSuffix);
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323 | if (node != null) {
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324 | if (!node.getFollowingSymbols().isEmpty()) {
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325 | suffixFound = true;
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326 | }
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327 | }
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328 | if (!suffixFound) {
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329 | contextSuffix.remove(0);
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330 | }
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331 | }
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332 | }
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333 |
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334 | return contextSuffix;
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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 | * used to recursively process the trie. The provided processor will be called for any path
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340 | * through the trie. The processor may abort the processing through return values of its
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341 | * {@link TrieProcessor#process(List, int)} method.
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342 | * </p>
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343 | *
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344 | * @param processor the processor to process the tree
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345 | */
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346 | public void process(TrieProcessor<T> processor) {
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347 | LinkedList<T> context = new LinkedList<T>();
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348 |
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349 | for (TrieNode<T> child : rootNode.getChildren()) {
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350 | if (!process(context, child, processor)) {
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351 | break;
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352 | }
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353 | }
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354 | }
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355 |
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356 | /**
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357 | * <p>
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358 | * processes a specific path by calling the provided processor. Furthermore, the method
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359 | * calls itself recursively for further subpaths.
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360 | * </p>
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361 | *
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362 | * @param context the context of the currently processed trie node, i.e. the preceding
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363 | * symbols
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364 | * @param child the processed trie node
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365 | * @param processor the processor used for processing the trie
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366 | *
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367 | * @return true, if processing shall continue, false else
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368 | */
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369 | private boolean process(LinkedList<T> context,
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370 | TrieNode<T> node,
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371 | TrieProcessor<T> processor)
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372 | {
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373 | context.add(node.getSymbol());
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374 |
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375 | TrieProcessor.Result result = processor.process(context, node.getCount());
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376 |
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377 | if (result == TrieProcessor.Result.CONTINUE) {
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378 | for (TrieNode<T> child : node.getChildren()) {
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379 | if (!process(context, child, processor)) {
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380 | break;
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381 | }
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382 | }
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383 | }
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384 |
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385 | context.removeLast();
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386 |
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387 | return result != TrieProcessor.Result.BREAK;
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388 | }
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389 |
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390 | /**
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391 | * <p>
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392 | * returns a list of symbol sequences which have a minimal length and that occurred as often
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393 | * as defined by the given occurrence count. If the given occurrence count is smaller 1 then
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394 | * those sequences are returned, that occur most often. The resulting list is empty, if there
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395 | * is no symbol sequence with the minimal length or the provided number of occurrences.
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396 | * </p>
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397 | *
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398 | * @param minimalLength the minimal length of the returned sequences
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399 | * @param occurrenceCount the number of occurrences of the returned sequences
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400 | *
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401 | * @return as described
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402 | */
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403 | public Collection<List<T>> getSequencesWithOccurrenceCount(int minimalLength,
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404 | int occurrenceCount)
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405 | {
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406 | LinkedList<TrieNode<T>> context = new LinkedList<TrieNode<T>>();
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407 | Collection<List<TrieNode<T>>> paths = new LinkedList<List<TrieNode<T>>>();
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408 |
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409 | context.push(rootNode);
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410 |
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411 | // traverse the trie and determine all sequences, which have the provided number of
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412 | // occurrences and a minimal length.
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413 |
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414 | // minimalLength + 1 because we denote the depth including the root node
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415 | determineLongPathsWithMostOccurrences(minimalLength + 1, occurrenceCount, paths, context);
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416 |
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417 | Collection<List<T>> resultingPaths = new LinkedList<List<T>>();
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418 | List<T> resultingPath;
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419 |
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420 | if (paths.size() > 0) {
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421 |
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422 | for (List<TrieNode<T>> path : paths) {
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423 | resultingPath = new LinkedList<T>();
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424 |
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425 | for (TrieNode<T> node : path) {
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426 | if (node.getSymbol() != null) {
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427 | resultingPath.add(node.getSymbol());
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428 | }
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429 | }
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430 |
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431 | resultingPaths.add(resultingPath);
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432 | }
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433 | }
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434 |
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435 | return resultingPaths;
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436 | }
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437 |
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438 | /**
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439 | * <p>
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440 | * Traverses the trie to collect all sequences with a defined number of occurrences and with
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441 | * a minimal length. If the given occurrence count is smaller 1 then those sequences are
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442 | * searched that occur most often. The length of the sequences is encoded in the provided
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443 | * recursion depth.
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444 | * </p>
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445 | *
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446 | * @param minimalDepth the minimal recursion depth to be done
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447 | * @param occurrenceCount the number of occurrences of the returned sequences
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448 | * @param paths the paths through the trie that all occurred with the same amount
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449 | * (if occurrence count is smaller 1, the paths which occurred most
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450 | * often) and that have the so far found matching number of occurrences
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451 | * (is updated each time a further path with the same number of
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452 | * occurrences is found; if occurrence count is smaller 1
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453 | * it is replaced if a path with more occurrences is found)
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454 | * @param context the path through the trie, that is analyzed by the recursive call
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455 | */
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456 | private void determineLongPathsWithMostOccurrences(int minimalDepth,
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457 | int occurrenceCount,
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458 | Collection<List<TrieNode<T>>> paths,
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459 | LinkedList<TrieNode<T>> context)
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460 | {
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461 | int envisagedCount = occurrenceCount;
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462 |
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463 | // only if we already reached the depth to be achieved, we check if the paths have the
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464 | // required number of occurrences
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465 | if (context.size() >= minimalDepth) {
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466 |
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467 | if (envisagedCount < 1) {
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468 | // try to determine the maximum number of occurrences so far, if any
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469 | if (paths.size() > 0) {
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470 | List<TrieNode<T>> path = paths.iterator().next();
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471 | envisagedCount = path.get(path.size() - 1).getCount();
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472 | }
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473 |
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474 | // if the current path has a higher number of occurrences than all so far, clear
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475 | // the paths collected so far and set the new number of occurrences as new maximum
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476 | if (context.getLast().getCount() > envisagedCount) {
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477 | paths.clear();
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478 | envisagedCount = context.getLast().getCount();
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479 | }
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480 | }
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481 |
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482 | // if the path matches the current maximal number of occurrences, add it to the list
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483 | // of collected paths with these number of occurrences
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484 | if (context.getLast().getCount() == envisagedCount) {
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485 | paths.add(new LinkedList<TrieNode<T>>(context));
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486 | }
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487 | }
|
---|
488 |
|
---|
489 | // perform the trie traversal
|
---|
490 | for (TrieNode<T> child : context.getLast().getChildren()) {
|
---|
491 | if (child.getCount() >= envisagedCount) {
|
---|
492 | context.add(child);
|
---|
493 | determineLongPathsWithMostOccurrences
|
---|
494 | (minimalDepth, occurrenceCount, paths, context);
|
---|
495 | context.removeLast();
|
---|
496 | }
|
---|
497 | }
|
---|
498 | }
|
---|
499 |
|
---|
500 | /**
|
---|
501 | * <p>
|
---|
502 | * adds a new symbol to the collection of known symbols if this symbol is not already
|
---|
503 | * contained.
|
---|
504 | * </p>
|
---|
505 | *
|
---|
506 | * @param symbol the symbol to be added to the known symbols
|
---|
507 | */
|
---|
508 | private void addToKnownSymbols(T symbol) {
|
---|
509 | if (!knownSymbols.containsSymbol(symbol)) {
|
---|
510 | knownSymbols.addSymbol(symbol, null);
|
---|
511 | }
|
---|
512 | }
|
---|
513 |
|
---|
514 | /**
|
---|
515 | * <p>
|
---|
516 | * Helper class for graph visualization of a trie.
|
---|
517 | * </p>
|
---|
518 | *
|
---|
519 | * @author Steffen Herbold
|
---|
520 | * @version 1.0
|
---|
521 | */
|
---|
522 | static public class Edge {}
|
---|
523 |
|
---|
524 | /**
|
---|
525 | * <p>
|
---|
526 | * Helper class for graph visualization of a trie.
|
---|
527 | * </p>
|
---|
528 | *
|
---|
529 | * @author Steffen Herbold
|
---|
530 | * @version 1.0
|
---|
531 | */
|
---|
532 | static public class TrieVertex {
|
---|
533 |
|
---|
534 | /**
|
---|
535 | * <p>
|
---|
536 | * Id of the vertex.
|
---|
537 | * </p>
|
---|
538 | */
|
---|
539 | private String id;
|
---|
540 |
|
---|
541 | /**
|
---|
542 | * <p>
|
---|
543 | * Constructor. Creates a new TrieVertex.
|
---|
544 | * </p>
|
---|
545 | *
|
---|
546 | * @param id
|
---|
547 | * id of the vertex
|
---|
548 | */
|
---|
549 | protected TrieVertex(String id) {
|
---|
550 | this.id = id;
|
---|
551 | }
|
---|
552 |
|
---|
553 | /**
|
---|
554 | * <p>
|
---|
555 | * Returns the id of the vertex.
|
---|
556 | * </p>
|
---|
557 | *
|
---|
558 | * @see java.lang.Object#toString()
|
---|
559 | */
|
---|
560 | @Override
|
---|
561 | public String toString() {
|
---|
562 | return id;
|
---|
563 | }
|
---|
564 | }
|
---|
565 |
|
---|
566 | /**
|
---|
567 | * <p>
|
---|
568 | * Returns a {@link Graph} representation of the trie.
|
---|
569 | * </p>
|
---|
570 | *
|
---|
571 | * @return {@link Graph} representation of the trie
|
---|
572 | */
|
---|
573 | protected Tree<TrieVertex, Edge> getGraph() {
|
---|
574 | DelegateTree<TrieVertex, Edge> graph = new DelegateTree<TrieVertex, Edge>();
|
---|
575 | rootNode.getGraph(null, graph);
|
---|
576 | return graph;
|
---|
577 | }
|
---|
578 |
|
---|
579 | /*
|
---|
580 | * (non-Javadoc)
|
---|
581 | *
|
---|
582 | * @see de.ugoe.cs.autoquest.usageprofiles.IDotCompatible#getDotRepresentation()
|
---|
583 | */
|
---|
584 | public String getDotRepresentation() {
|
---|
585 | StringBuilder stringBuilder = new StringBuilder();
|
---|
586 | stringBuilder.append("digraph model {" + StringTools.ENDLINE);
|
---|
587 | rootNode.appendDotRepresentation(stringBuilder);
|
---|
588 | stringBuilder.append('}' + StringTools.ENDLINE);
|
---|
589 | return stringBuilder.toString();
|
---|
590 | }
|
---|
591 |
|
---|
592 | /**
|
---|
593 | * <p>
|
---|
594 | * Returns the string representation of the root node.
|
---|
595 | * </p>
|
---|
596 | *
|
---|
597 | * @see TrieNode#toString()
|
---|
598 | * @see java.lang.Object#toString()
|
---|
599 | */
|
---|
600 | @Override
|
---|
601 | public String toString() {
|
---|
602 | return rootNode.toString();
|
---|
603 | }
|
---|
604 |
|
---|
605 | /**
|
---|
606 | * <p>
|
---|
607 | * Returns the number of symbols contained in the trie.
|
---|
608 | * </p>
|
---|
609 | *
|
---|
610 | * @return number of symbols contained in the trie
|
---|
611 | */
|
---|
612 | public int getNumSymbols() {
|
---|
613 | return knownSymbols.size();
|
---|
614 | }
|
---|
615 |
|
---|
616 | /**
|
---|
617 | * <p>
|
---|
618 | * Returns the number of trie nodes that are ancestors of a leaf. This is the equivalent to the
|
---|
619 | * number of states a first-order markov model would have.
|
---|
620 | * <p>
|
---|
621 | *
|
---|
622 | * @return number of trie nodes that are ancestors of leafs.
|
---|
623 | */
|
---|
624 | public int getNumLeafAncestors() {
|
---|
625 | List<TrieNode<T>> ancestors = new LinkedList<TrieNode<T>>();
|
---|
626 | rootNode.getLeafAncestors(ancestors);
|
---|
627 | return ancestors.size();
|
---|
628 | }
|
---|
629 |
|
---|
630 | /**
|
---|
631 | * <p>
|
---|
632 | * Returns the number of trie nodes that are leafs.
|
---|
633 | * </p>
|
---|
634 | *
|
---|
635 | * @return number of leafs in the trie
|
---|
636 | */
|
---|
637 | public int getNumLeafs() {
|
---|
638 | return rootNode.getNumLeafs();
|
---|
639 | }
|
---|
640 |
|
---|
641 | /**
|
---|
642 | * <p>
|
---|
643 | * Updates the list of known symbols by replacing it with all symbols that are found in the
|
---|
644 | * child nodes of the root node. This should be the same as all symbols that are contained in
|
---|
645 | * the trie.
|
---|
646 | * </p>
|
---|
647 | */
|
---|
648 | public void updateKnownSymbols() {
|
---|
649 | knownSymbols = strategy.createSymbolMap();
|
---|
650 | for (TrieNode<T> node : rootNode.getChildren()) {
|
---|
651 | addToKnownSymbols(node.getSymbol());
|
---|
652 | }
|
---|
653 | }
|
---|
654 |
|
---|
655 | /**
|
---|
656 | * <p>
|
---|
657 | * Two tries are defined as equal, if their {@link #rootNode}s are equal.
|
---|
658 | * </p>
|
---|
659 | *
|
---|
660 | * @see java.lang.Object#equals(java.lang.Object)
|
---|
661 | */
|
---|
662 | @SuppressWarnings("rawtypes")
|
---|
663 | @Override
|
---|
664 | public boolean equals(Object other) {
|
---|
665 | if (other == this) {
|
---|
666 | return true;
|
---|
667 | }
|
---|
668 | if (other instanceof Trie) {
|
---|
669 | return rootNode.equals(((Trie) other).rootNode);
|
---|
670 | }
|
---|
671 | return false;
|
---|
672 | }
|
---|
673 |
|
---|
674 | /*
|
---|
675 | * (non-Javadoc)
|
---|
676 | *
|
---|
677 | * @see java.lang.Object#hashCode()
|
---|
678 | */
|
---|
679 | @Override
|
---|
680 | public int hashCode() {
|
---|
681 | int multiplier = 17;
|
---|
682 | int hash = 42;
|
---|
683 | if (rootNode != null) {
|
---|
684 | hash = multiplier * hash + rootNode.hashCode();
|
---|
685 | }
|
---|
686 | return hash;
|
---|
687 | }
|
---|
688 |
|
---|
689 | }
|
---|