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.HashSet;
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20 | import java.util.LinkedHashSet;
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21 | import java.util.LinkedList;
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22 | import java.util.List;
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23 |
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24 | import de.ugoe.cs.util.StringTools;
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25 |
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26 | import edu.uci.ics.jung.graph.DelegateTree;
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27 | import edu.uci.ics.jung.graph.Graph;
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28 | import edu.uci.ics.jung.graph.Tree;
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29 |
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30 | /**
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31 | * <p>
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32 | * This class implements a <it>trie</it>, i.e., a tree of sequences that the occurence of
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33 | * subsequences up to a predefined length. This length is the trie order.
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34 | * </p>
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35 | *
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36 | * @author Steffen Herbold, Patrick Harms
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37 | *
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38 | * @param <T>
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39 | * Type of the symbols that are stored in the trie.
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40 | *
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41 | * @see TrieNode
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42 | */
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43 | public class Trie<T> implements IDotCompatible, Serializable {
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44 |
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45 | /**
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46 | * <p>
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47 | * Id for object serialization.
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48 | * </p>
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49 | */
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50 | private static final long serialVersionUID = 1L;
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51 |
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52 | /**
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53 | * <p>
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54 | * Collection of all symbols occuring in the trie.
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55 | * </p>
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56 | */
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57 | private Collection<T> knownSymbols;
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58 |
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59 | /**
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60 | * <p>
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61 | * Reference to the root of the trie.
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62 | * </p>
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63 | */
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64 | private final TrieNode<T> rootNode;
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65 |
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66 | /**
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67 | * <p>
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68 | * Comparator to be used for comparing the symbols with each other
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69 | * </p>
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70 | */
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71 | private SymbolComparator<T> comparator;
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72 |
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73 | /**
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74 | * <p>
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75 | * Contructor. Creates a new Trie with a {@link DefaultSymbolComparator}.
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76 | * </p>
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77 | */
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78 | public Trie() {
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79 | this(new DefaultSymbolComparator<T>());
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80 | }
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81 |
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82 | /**
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83 | * <p>
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84 | * Contructor. Creates a new Trie with that uses a specific {@link SymbolComparator}.
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85 | * </p>
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86 | */
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87 | public Trie(SymbolComparator<T> comparator) {
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88 | this.comparator = comparator;
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89 | rootNode = new TrieNode<T>(comparator);
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90 | knownSymbols = new LinkedHashSet<T>();
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91 | }
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92 |
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93 | /**
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94 | * <p>
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95 | * Copy-Constructor. Creates a new Trie as the copy of other. The other trie must not be null.
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96 | * </p>
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97 | *
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98 | * @param other
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99 | * Trie that is copied
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100 | */
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101 | public Trie(Trie<T> other) {
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102 | if (other == null) {
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103 | throw new IllegalArgumentException("other trie must not be null");
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104 | }
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105 | rootNode = new TrieNode<T>(other.rootNode);
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106 | knownSymbols = new LinkedHashSet<T>(other.knownSymbols);
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107 | comparator = other.comparator;
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108 | }
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109 |
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110 | /**
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111 | * <p>
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112 | * Returns a collection of all symbols occuring in the trie.
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113 | * </p>
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114 | *
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115 | * @return symbols occuring in the trie
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116 | */
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117 | public Collection<T> getKnownSymbols() {
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118 | return new LinkedHashSet<T>(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 | * Trains the current trie using the given sequence and adds all subsequence of length
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124 | * {@code maxOrder}.
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125 | * </p>
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126 | *
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127 | * @param sequence
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128 | * sequence whose subsequences are added to the trie
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129 | * @param maxOrder
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130 | * maximum length of the subsequences added to the trie
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131 | */
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132 | public void train(List<T> sequence, int maxOrder) {
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133 | if (maxOrder < 1) {
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134 | return;
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135 | }
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136 | IncompleteMemory<T> latestActions = new IncompleteMemory<T>(maxOrder);
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137 | int i = 0;
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138 | for (T currentEvent : sequence) {
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139 | latestActions.add(currentEvent);
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140 | addToKnownSymbols(currentEvent);
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141 | i++;
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142 | if (i >= maxOrder) {
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143 | add(latestActions.getLast(maxOrder));
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144 | }
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145 | }
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146 | int sequenceLength = sequence.size();
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147 | for (int j = maxOrder - 1; j > 0; j--) {
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148 | add(sequence.subList(sequenceLength - j, sequenceLength));
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149 | }
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150 | }
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151 |
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152 | /**
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153 | * <p>
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154 | * Adds a given subsequence to the trie and increases the counters accordingly.
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155 | * </p>
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156 | *
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157 | * @param subsequence
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158 | * subsequence whose counters are increased
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159 | * @see TrieNode#add(List)
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160 | */
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161 | protected void add(List<T> subsequence) {
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162 | if (subsequence != null && !subsequence.isEmpty()) {
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163 | addToKnownSymbols(subsequence);
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164 | subsequence = new LinkedList<T>(subsequence); // defensive copy!
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165 | T firstSymbol = subsequence.get(0);
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166 | TrieNode<T> node = getChildCreate(firstSymbol);
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167 | node.add(subsequence);
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168 | }
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169 | }
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170 |
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171 | /**
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172 | * <p>
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173 | * Returns the child of the root node associated with the given symbol or creates it if it does
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174 | * not exist yet.
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175 | * </p>
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176 | *
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177 | * @param symbol
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178 | * symbol whose node is required
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179 | * @return node associated with the symbol
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180 | * @see TrieNode#getChildCreate(Object)
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181 | */
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182 | protected TrieNode<T> getChildCreate(T symbol) {
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183 | return rootNode.getChildCreate(symbol);
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184 | }
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185 |
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186 | /**
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187 | * <p>
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188 | * Returns the child of the root node associated with the given symbol or null if it does not
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189 | * exist.
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190 | * </p>
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191 | *
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192 | * @param symbol
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193 | * symbol whose node is required
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194 | * @return node associated with the symbol; null if no such node exists
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195 | * @see TrieNode#getChild(Object)
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196 | */
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197 | protected TrieNode<T> getChild(T symbol) {
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198 | return rootNode.getChild(symbol);
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199 | }
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200 |
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201 | /**
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202 | * <p>
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203 | * Returns the number of occurences of the given sequence.
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204 | * </p>
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205 | *
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206 | * @param sequence
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207 | * sequence whose number of occurences is required
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208 | * @return number of occurences of the sequence
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209 | */
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210 | public int getCount(List<T> sequence) {
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211 | int count = 0;
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212 | TrieNode<T> node = find(sequence);
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213 | if (node != null) {
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214 | count = node.getCount();
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215 | }
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216 | return count;
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217 | }
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218 |
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219 | /**
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220 | * <p>
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221 | * Returns the number of occurences of the given prefix and a symbol that follows it.<br>
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222 | * Convenience function to simplify usage of {@link #getCount(List)}.
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223 | * </p>
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224 | *
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225 | * @param sequence
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226 | * prefix of the sequence
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227 | * @param follower
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228 | * suffix of the sequence
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229 | * @return number of occurences of the sequence
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230 | * @see #getCount(List)
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231 | */
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232 | public int getCount(List<T> sequence, T follower) {
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233 | List<T> tmpSequence = new LinkedList<T>(sequence);
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234 | tmpSequence.add(follower);
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235 | return getCount(tmpSequence);
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236 |
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237 | }
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238 |
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239 | /**
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240 | * <p>
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241 | * Searches the trie for a given sequence and returns the node associated with the sequence or
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242 | * null if no such node is found.
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243 | * </p>
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244 | *
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245 | * @param sequence
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246 | * sequence that is searched for
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247 | * @return node associated with the sequence
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248 | * @see TrieNode#find(List)
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249 | */
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250 | public TrieNode<T> find(List<T> sequence) {
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251 | if (sequence == null || sequence.isEmpty()) {
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252 | return rootNode;
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253 | }
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254 | List<T> sequenceCopy = new LinkedList<T>(sequence);
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255 | TrieNode<T> result = null;
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256 | TrieNode<T> node = getChild(sequenceCopy.get(0));
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257 | if (node != null) {
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258 | sequenceCopy.remove(0);
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259 | result = node.find(sequenceCopy);
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260 | }
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261 | return result;
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262 | }
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263 |
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264 | /**
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265 | * <p>
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266 | * Returns a collection of all symbols that follow a given sequence in the trie. In case the
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267 | * sequence is not found or no symbols follow the sequence the result will be empty.
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268 | * </p>
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269 | *
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270 | * @param sequence
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271 | * sequence whose followers are returned
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272 | * @return symbols following the given sequence
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273 | * @see TrieNode#getFollowingSymbols()
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274 | */
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275 | public Collection<T> getFollowingSymbols(List<T> sequence) {
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276 | Collection<T> result = new LinkedList<T>();
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277 | TrieNode<T> node = find(sequence);
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278 | if (node != null) {
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279 | result = node.getFollowingSymbols();
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280 | }
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281 | return result;
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282 | }
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283 |
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284 | /**
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285 | * <p>
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286 | * Returns the longest suffix of the given context that is contained in the tree and whose
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287 | * children are leaves.
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288 | * </p>
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289 | *
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290 | * @param context
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291 | * context whose suffix is searched for
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292 | * @return longest suffix of the context
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293 | */
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294 | public List<T> getContextSuffix(List<T> context) {
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295 | List<T> contextSuffix;
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296 | if (context != null) {
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297 | contextSuffix = new LinkedList<T>(context); // defensive copy
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298 | }
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299 | else {
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300 | contextSuffix = new LinkedList<T>();
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301 | }
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302 | boolean suffixFound = false;
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303 |
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304 | while (!suffixFound) {
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305 | if (contextSuffix.isEmpty()) {
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306 | suffixFound = true; // suffix is the empty word
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307 | }
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308 | else {
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309 | TrieNode<T> node = find(contextSuffix);
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310 | if (node != null) {
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311 | if (!node.getFollowingSymbols().isEmpty()) {
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312 | suffixFound = true;
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313 | }
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314 | }
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315 | if (!suffixFound) {
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316 | contextSuffix.remove(0);
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317 | }
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318 | }
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319 | }
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320 |
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321 | return contextSuffix;
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322 | }
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323 |
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324 | /**
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325 | * <p>
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326 | * returns a list of symbol sequences which have a minimal length and that occurred most often
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327 | * with the same number of occurrences. The resulting list is empty, if there is no symbol
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328 | * sequence with the minimal length.
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329 | * </p>
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330 | *
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331 | * @param minimalLength the minimal length of the returned sequences
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332 | *
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333 | * @return as described
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334 | */
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335 | public Collection<List<T>> getSequencesWithMostOccurrences(int minimalLength) {
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336 | LinkedList<TrieNode<T>> context = new LinkedList<TrieNode<T>>();
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337 | Collection<List<TrieNode<T>>> paths = new LinkedList<List<TrieNode<T>>>();
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338 |
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339 | context.push(rootNode);
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340 |
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341 | // traverse the trie and determine all sequences, which have the maximum number of
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342 | // occurrences and a minimal length.
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343 |
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344 | // minimalLength + 1 because we denote the depth including the root node
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345 | determineLongPathsWithMostOccurrences(minimalLength + 1, paths, context);
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346 |
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347 | Collection<List<T>> resultingPaths = new LinkedList<List<T>>();
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348 | List<T> resultingPath;
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349 |
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350 | if (paths.size() > 0) {
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351 |
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352 | for (List<TrieNode<T>> path : paths) {
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353 | resultingPath = new LinkedList<T>();
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354 |
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355 | for (TrieNode<T> node : path) {
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356 | if (node.getSymbol() != null) {
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357 | resultingPath.add(node.getSymbol());
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358 | }
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359 | }
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360 |
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361 | resultingPaths.add(resultingPath);
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362 | }
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363 | }
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364 |
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365 | return resultingPaths;
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366 | }
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367 |
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368 | /**
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369 | * <p>
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370 | * Traverses the trie to collect all sequences with a maximum number of occurrences and with
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371 | * a minimal length. The length is encoded in the provided recursion depth.
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372 | * </p>
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373 | *
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374 | * @param minimalDepth the minimal recursion depth to be done
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375 | * @param paths the paths through the trie that all occurred with the same amount and
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376 | * that have the so far found maximum of occurrences (is updated each
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377 | * time a further path with the same number of occurrences is found; is
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378 | * replaced if a path with more occurrences is found)
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379 | * @param context the path through the trie, that is analyzed by the recursive call
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380 | */
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381 | private void determineLongPathsWithMostOccurrences(int minimalDepth,
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382 | Collection<List<TrieNode<T>>> paths,
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383 | LinkedList<TrieNode<T>> context)
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384 | {
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385 | int maxCount = 0;
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386 |
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387 | // only if we already reached the depth to be achieved, we check if the paths have the
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388 | // maximum number of occurrences
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389 | if (context.size() >= minimalDepth) {
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390 |
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391 | // try to determine the maximum number of occurrences so far, if any
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392 | if (paths.size() > 0) {
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393 | List<TrieNode<T>> path = paths.iterator().next();
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394 | maxCount = path.get(path.size() - 1).getCount();
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395 | }
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396 |
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397 | // if the current path has a higher number of occurrences than all so far, clear
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398 | // the paths collected so far and set the new number of occurrences as new maximum
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399 | if (context.getLast().getCount() > maxCount) {
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400 | paths.clear();
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401 | maxCount = context.getLast().getCount();
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402 | }
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403 |
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404 | // if the path matches the current maximal number of occurrences, add it to the list
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405 | // of collected paths with these number of occurrences
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406 | if (context.getLast().getCount() == maxCount) {
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407 | paths.add(new LinkedList<TrieNode<T>>(context));
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408 | }
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409 | }
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410 |
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411 | // perform the trie traversal
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412 | for (TrieNode<T> child : context.getLast().getChildren()) {
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413 | if (child.getCount() >= maxCount) {
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414 | context.add(child);
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415 | determineLongPathsWithMostOccurrences(minimalDepth, paths, context);
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416 | context.removeLast();
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417 | }
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418 | }
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419 | }
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420 |
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421 | /**
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422 | * <p>
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423 | * adds a new symbol to the collection of known symbols if this symbol is not already
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424 | * contained. The symbols are compared using the comparator.
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425 | * </p>
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426 | *
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427 | * @param symbol the symbol to be added to the known symbols
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428 | */
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429 | private void addToKnownSymbols(T symbol) {
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430 | for (T knownSymbol : knownSymbols) {
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431 | if (comparator.equals(knownSymbol, symbol)) {
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432 | return;
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433 | }
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434 | }
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435 |
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436 | knownSymbols.add(symbol);
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437 | }
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438 |
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439 | /**
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440 | * <p>
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441 | * adds a list of new symbols to the collection of known symbols. Uses the
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442 | * {@link #addToKnownSymbols(Object)} method for each element of the provided list.
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443 | * </p>
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444 | *
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445 | * @param symbols the list of symbols to be added to the known symbols
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446 | */
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447 | private void addToKnownSymbols(List<T> symbols) {
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448 | for (T symbol : symbols) {
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449 | addToKnownSymbols(symbol);
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450 | }
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451 | }
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452 |
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453 | /**
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454 | * <p>
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455 | * Helper class for graph visualization of a trie.
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456 | * </p>
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457 | *
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458 | * @author Steffen Herbold
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459 | * @version 1.0
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460 | */
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461 | static public class Edge {}
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462 |
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463 | /**
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464 | * <p>
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465 | * Helper class for graph visualization of a trie.
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466 | * </p>
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467 | *
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468 | * @author Steffen Herbold
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469 | * @version 1.0
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470 | */
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471 | static public class TrieVertex {
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472 |
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473 | /**
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474 | * <p>
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475 | * Id of the vertex.
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476 | * </p>
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477 | */
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478 | private String id;
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479 |
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480 | /**
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481 | * <p>
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482 | * Contructor. Creates a new TrieVertex.
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483 | * </p>
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484 | *
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485 | * @param id
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486 | * id of the vertex
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487 | */
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488 | protected TrieVertex(String id) {
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489 | this.id = id;
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490 | }
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491 |
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492 | /**
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493 | * <p>
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494 | * Returns the id of the vertex.
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495 | * </p>
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496 | *
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497 | * @see java.lang.Object#toString()
|
---|
498 | */
|
---|
499 | @Override
|
---|
500 | public String toString() {
|
---|
501 | return id;
|
---|
502 | }
|
---|
503 | }
|
---|
504 |
|
---|
505 | /**
|
---|
506 | * <p>
|
---|
507 | * Returns a {@link Graph} representation of the trie.
|
---|
508 | * </p>
|
---|
509 | *
|
---|
510 | * @return {@link Graph} representation of the trie
|
---|
511 | */
|
---|
512 | protected Tree<TrieVertex, Edge> getGraph() {
|
---|
513 | DelegateTree<TrieVertex, Edge> graph = new DelegateTree<TrieVertex, Edge>();
|
---|
514 | rootNode.getGraph(null, graph);
|
---|
515 | return graph;
|
---|
516 | }
|
---|
517 |
|
---|
518 | /*
|
---|
519 | * (non-Javadoc)
|
---|
520 | *
|
---|
521 | * @see de.ugoe.cs.autoquest.usageprofiles.IDotCompatible#getDotRepresentation()
|
---|
522 | */
|
---|
523 | public String getDotRepresentation() {
|
---|
524 | StringBuilder stringBuilder = new StringBuilder();
|
---|
525 | stringBuilder.append("digraph model {" + StringTools.ENDLINE);
|
---|
526 | rootNode.appendDotRepresentation(stringBuilder);
|
---|
527 | stringBuilder.append('}' + StringTools.ENDLINE);
|
---|
528 | return stringBuilder.toString();
|
---|
529 | }
|
---|
530 |
|
---|
531 | /**
|
---|
532 | * <p>
|
---|
533 | * Returns the string representation of the root node.
|
---|
534 | * </p>
|
---|
535 | *
|
---|
536 | * @see TrieNode#toString()
|
---|
537 | * @see java.lang.Object#toString()
|
---|
538 | */
|
---|
539 | @Override
|
---|
540 | public String toString() {
|
---|
541 | return rootNode.toString();
|
---|
542 | }
|
---|
543 |
|
---|
544 | /**
|
---|
545 | * <p>
|
---|
546 | * Returns the number of symbols contained in the trie.
|
---|
547 | * </p>
|
---|
548 | *
|
---|
549 | * @return number of symbols contained in the trie
|
---|
550 | */
|
---|
551 | public int getNumSymbols() {
|
---|
552 | return knownSymbols.size();
|
---|
553 | }
|
---|
554 |
|
---|
555 | /**
|
---|
556 | * <p>
|
---|
557 | * Returns the number of trie nodes that are ancestors of a leaf. This is the equivalent to the
|
---|
558 | * number of states a first-order markov model would have.
|
---|
559 | * <p>
|
---|
560 | *
|
---|
561 | * @return number of trie nodes that are ancestors of leafs.
|
---|
562 | */
|
---|
563 | public int getNumLeafAncestors() {
|
---|
564 | List<TrieNode<T>> ancestors = new LinkedList<TrieNode<T>>();
|
---|
565 | rootNode.getLeafAncestors(ancestors);
|
---|
566 | return ancestors.size();
|
---|
567 | }
|
---|
568 |
|
---|
569 | /**
|
---|
570 | * <p>
|
---|
571 | * Returns the number of trie nodes that are leafs.
|
---|
572 | * </p>
|
---|
573 | *
|
---|
574 | * @return number of leafs in the trie
|
---|
575 | */
|
---|
576 | public int getNumLeafs() {
|
---|
577 | return rootNode.getNumLeafs();
|
---|
578 | }
|
---|
579 |
|
---|
580 | /**
|
---|
581 | * <p>
|
---|
582 | * Updates the list of known symbols by replacing it with all symbols that are found in the
|
---|
583 | * child nodes of the root node. This should be the same as all symbols that are contained in
|
---|
584 | * the trie.
|
---|
585 | * </p>
|
---|
586 | */
|
---|
587 | public void updateKnownSymbols() {
|
---|
588 | knownSymbols = new HashSet<T>();
|
---|
589 | for (TrieNode<T> node : rootNode.getChildren()) {
|
---|
590 | addToKnownSymbols(node.getSymbol());
|
---|
591 | }
|
---|
592 | }
|
---|
593 |
|
---|
594 | /**
|
---|
595 | * <p>
|
---|
596 | * Two Tries are defined as equal, if their {@link #rootNode} are equal.
|
---|
597 | * </p>
|
---|
598 | *
|
---|
599 | * @see java.lang.Object#equals(java.lang.Object)
|
---|
600 | */
|
---|
601 | @SuppressWarnings("rawtypes")
|
---|
602 | @Override
|
---|
603 | public boolean equals(Object other) {
|
---|
604 | if (other == this) {
|
---|
605 | return true;
|
---|
606 | }
|
---|
607 | if (other instanceof Trie) {
|
---|
608 | return rootNode.equals(((Trie) other).rootNode);
|
---|
609 | }
|
---|
610 | return false;
|
---|
611 | }
|
---|
612 |
|
---|
613 | /*
|
---|
614 | * (non-Javadoc)
|
---|
615 | *
|
---|
616 | * @see java.lang.Object#hashCode()
|
---|
617 | */
|
---|
618 | @Override
|
---|
619 | public int hashCode() {
|
---|
620 | int multiplier = 17;
|
---|
621 | int hash = 42;
|
---|
622 | if (rootNode != null) {
|
---|
623 | hash = multiplier * hash + rootNode.hashCode();
|
---|
624 | }
|
---|
625 | return hash;
|
---|
626 | }
|
---|
627 |
|
---|
628 | }
|
---|