[518] | 1 | package de.ugoe.cs.quest.usageprofiles;
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| 2 |
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| 3 | import java.io.Serializable;
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| 4 | import java.util.Collection;
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| 5 | import java.util.HashSet;
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| 6 | import java.util.LinkedHashSet;
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| 7 | import java.util.LinkedList;
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| 8 | import java.util.List;
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| 9 |
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| 10 | import de.ugoe.cs.util.StringTools;
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| 11 |
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| 12 | import edu.uci.ics.jung.graph.DelegateTree;
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| 13 | import edu.uci.ics.jung.graph.Graph;
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| 14 | import edu.uci.ics.jung.graph.Tree;
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| 15 |
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| 16 | /**
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| 17 | * <p>
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[559] | 18 | * This class implements a <it>trie</it>, i.e., a tree of sequences that the occurence of
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| 19 | * subsequences up to a predefined length. This length is the trie order.
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[518] | 20 | * </p>
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| 21 | *
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| 22 | * @author Steffen Herbold
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| 23 | *
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| 24 | * @param <T>
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| 25 | * Type of the symbols that are stored in the trie.
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| 26 | *
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| 27 | * @see TrieNode
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| 28 | */
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| 29 | public class Trie<T> implements IDotCompatible, Serializable {
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| 30 |
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[559] | 31 | /**
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| 32 | * <p>
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| 33 | * Id for object serialization.
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| 34 | * </p>
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| 35 | */
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| 36 | private static final long serialVersionUID = 1L;
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[518] | 37 |
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[559] | 38 | /**
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| 39 | * <p>
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| 40 | * Collection of all symbols occuring in the trie.
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| 41 | * </p>
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| 42 | */
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| 43 | private Collection<T> knownSymbols;
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[518] | 44 |
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[559] | 45 | /**
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| 46 | * <p>
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| 47 | * Reference to the root of the trie.
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| 48 | * </p>
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| 49 | */
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| 50 | private final TrieNode<T> rootNode;
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[518] | 51 |
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[559] | 52 | /**
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| 53 | * <p>
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| 54 | * Contructor. Creates a new Trie.
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| 55 | * </p>
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| 56 | */
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| 57 | public Trie() {
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| 58 | rootNode = new TrieNode<T>();
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| 59 | knownSymbols = new LinkedHashSet<T>();
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| 60 | }
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[518] | 61 |
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[559] | 62 | /**
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| 63 | * <p>
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| 64 | * Copy-Constructor. Creates a new Trie as the copy of other. The other trie must noch be null.
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| 65 | * </p>
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| 66 | *
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| 67 | * @param other
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| 68 | * Trie that is copied
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| 69 | */
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| 70 | public Trie(Trie<T> other) {
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| 71 | if (other == null) {
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[766] | 72 | throw new IllegalArgumentException("other trie must not be null");
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[559] | 73 | }
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| 74 | rootNode = new TrieNode<T>(other.rootNode);
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| 75 | knownSymbols = new LinkedHashSet<T>(other.knownSymbols);
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| 76 | }
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[518] | 77 |
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[559] | 78 | /**
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| 79 | * <p>
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| 80 | * Returns a collection of all symbols occuring in the trie.
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| 81 | * </p>
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| 82 | *
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| 83 | * @return symbols occuring in the trie
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| 84 | */
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| 85 | public Collection<T> getKnownSymbols() {
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| 86 | return new LinkedHashSet<T>(knownSymbols);
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| 87 | }
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[518] | 88 |
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[559] | 89 | /**
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| 90 | * <p>
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| 91 | * Trains the current trie using the given sequence and adds all subsequence of length
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| 92 | * {@code maxOrder}.
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| 93 | * </p>
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| 94 | *
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| 95 | * @param sequence
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| 96 | * sequence whose subsequences are added to the trie
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| 97 | * @param maxOrder
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| 98 | * maximum length of the subsequences added to the trie
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| 99 | */
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| 100 | public void train(List<T> sequence, int maxOrder) {
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| 101 | if (maxOrder < 1) {
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| 102 | return;
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| 103 | }
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| 104 | IncompleteMemory<T> latestActions = new IncompleteMemory<T>(maxOrder);
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| 105 | int i = 0;
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| 106 | for (T currentEvent : sequence) {
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| 107 | latestActions.add(currentEvent);
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| 108 | knownSymbols.add(currentEvent);
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| 109 | i++;
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| 110 | if (i >= maxOrder) {
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| 111 | add(latestActions.getLast(maxOrder));
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| 112 | }
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| 113 | }
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| 114 | int sequenceLength = sequence.size();
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| 115 | for (int j = maxOrder - 1; j > 0; j--) {
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| 116 | add(sequence.subList(sequenceLength - j, sequenceLength));
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| 117 | }
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| 118 | }
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[518] | 119 |
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[559] | 120 | /**
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| 121 | * <p>
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| 122 | * Adds a given subsequence to the trie and increases the counters accordingly.
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| 123 | * </p>
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| 124 | *
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| 125 | * @param subsequence
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| 126 | * subsequence whose counters are increased
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| 127 | * @see TrieNode#add(List)
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| 128 | */
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| 129 | protected void add(List<T> subsequence) {
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| 130 | if (subsequence != null && !subsequence.isEmpty()) {
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| 131 | knownSymbols.addAll(subsequence);
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| 132 | subsequence = new LinkedList<T>(subsequence); // defensive copy!
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| 133 | T firstSymbol = subsequence.get(0);
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| 134 | TrieNode<T> node = getChildCreate(firstSymbol);
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| 135 | node.add(subsequence);
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| 136 | }
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| 137 | }
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[518] | 138 |
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[559] | 139 | /**
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| 140 | * <p>
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| 141 | * Returns the child of the root node associated with the given symbol or creates it if it does
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| 142 | * not exist yet.
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| 143 | * </p>
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| 144 | *
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| 145 | * @param symbol
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| 146 | * symbol whose node is required
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| 147 | * @return node associated with the symbol
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| 148 | * @see TrieNode#getChildCreate(Object)
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| 149 | */
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| 150 | protected TrieNode<T> getChildCreate(T symbol) {
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| 151 | return rootNode.getChildCreate(symbol);
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| 152 | }
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[518] | 153 |
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[559] | 154 | /**
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| 155 | * <p>
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| 156 | * Returns the child of the root node associated with the given symbol or null if it does not
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| 157 | * exist.
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| 158 | * </p>
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| 159 | *
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| 160 | * @param symbol
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| 161 | * symbol whose node is required
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| 162 | * @return node associated with the symbol; null if no such node exists
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| 163 | * @see TrieNode#getChild(Object)
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| 164 | */
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| 165 | protected TrieNode<T> getChild(T symbol) {
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| 166 | return rootNode.getChild(symbol);
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| 167 | }
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[518] | 168 |
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[559] | 169 | /**
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| 170 | * <p>
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| 171 | * Returns the number of occurences of the given sequence.
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| 172 | * </p>
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| 173 | *
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| 174 | * @param sequence
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| 175 | * sequence whose number of occurences is required
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| 176 | * @return number of occurences of the sequence
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| 177 | */
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| 178 | public int getCount(List<T> sequence) {
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| 179 | int count = 0;
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| 180 | TrieNode<T> node = find(sequence);
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| 181 | if (node != null) {
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| 182 | count = node.getCount();
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| 183 | }
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| 184 | return count;
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| 185 | }
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[518] | 186 |
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[559] | 187 | /**
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| 188 | * <p>
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| 189 | * Returns the number of occurences of the given prefix and a symbol that follows it.<br>
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| 190 | * Convenience function to simplify usage of {@link #getCount(List)}.
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| 191 | * </p>
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| 192 | *
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| 193 | * @param sequence
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| 194 | * prefix of the sequence
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| 195 | * @param follower
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| 196 | * suffix of the sequence
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| 197 | * @return number of occurences of the sequence
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| 198 | * @see #getCount(List)
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| 199 | */
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| 200 | public int getCount(List<T> sequence, T follower) {
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| 201 | List<T> tmpSequence = new LinkedList<T>(sequence);
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| 202 | tmpSequence.add(follower);
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| 203 | return getCount(tmpSequence);
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[518] | 204 |
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[559] | 205 | }
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[518] | 206 |
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[559] | 207 | /**
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| 208 | * <p>
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| 209 | * Searches the trie for a given sequence and returns the node associated with the sequence or
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| 210 | * null if no such node is found.
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| 211 | * </p>
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| 212 | *
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| 213 | * @param sequence
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| 214 | * sequence that is searched for
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| 215 | * @return node associated with the sequence
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| 216 | * @see TrieNode#find(List)
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| 217 | */
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| 218 | public TrieNode<T> find(List<T> sequence) {
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| 219 | if (sequence == null || sequence.isEmpty()) {
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| 220 | return rootNode;
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| 221 | }
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| 222 | List<T> sequenceCopy = new LinkedList<T>(sequence);
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| 223 | TrieNode<T> result = null;
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| 224 | TrieNode<T> node = getChild(sequenceCopy.get(0));
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| 225 | if (node != null) {
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| 226 | sequenceCopy.remove(0);
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| 227 | result = node.find(sequenceCopy);
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| 228 | }
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| 229 | return result;
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| 230 | }
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[518] | 231 |
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[559] | 232 | /**
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| 233 | * <p>
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| 234 | * Returns a collection of all symbols that follow a given sequence in the trie. In case the
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| 235 | * sequence is not found or no symbols follow the sequence the result will be empty.
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| 236 | * </p>
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| 237 | *
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| 238 | * @param sequence
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| 239 | * sequence whose followers are returned
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| 240 | * @return symbols following the given sequence
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| 241 | * @see TrieNode#getFollowingSymbols()
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| 242 | */
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| 243 | public Collection<T> getFollowingSymbols(List<T> sequence) {
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| 244 | Collection<T> result = new LinkedList<T>();
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| 245 | TrieNode<T> node = find(sequence);
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| 246 | if (node != null) {
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| 247 | result = node.getFollowingSymbols();
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| 248 | }
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| 249 | return result;
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| 250 | }
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[518] | 251 |
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[559] | 252 | /**
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| 253 | * <p>
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| 254 | * Returns the longest suffix of the given context that is contained in the tree and whose
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| 255 | * children are leaves.
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| 256 | * </p>
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| 257 | *
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| 258 | * @param context
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| 259 | * context whose suffix is searched for
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| 260 | * @return longest suffix of the context
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| 261 | */
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| 262 | public List<T> getContextSuffix(List<T> context) {
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| 263 | List<T> contextSuffix;
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| 264 | if (context != null) {
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| 265 | contextSuffix = new LinkedList<T>(context); // defensive copy
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| 266 | }
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| 267 | else {
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| 268 | contextSuffix = new LinkedList<T>();
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| 269 | }
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| 270 | boolean suffixFound = false;
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[518] | 271 |
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[559] | 272 | while (!suffixFound) {
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| 273 | if (contextSuffix.isEmpty()) {
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| 274 | suffixFound = true; // suffix is the empty word
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| 275 | }
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| 276 | else {
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| 277 | TrieNode<T> node = find(contextSuffix);
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| 278 | if (node != null) {
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| 279 | if (!node.getFollowingSymbols().isEmpty()) {
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| 280 | suffixFound = true;
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| 281 | }
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| 282 | }
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| 283 | if (!suffixFound) {
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| 284 | contextSuffix.remove(0);
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| 285 | }
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| 286 | }
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| 287 | }
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[518] | 288 |
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[559] | 289 | return contextSuffix;
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| 290 | }
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[518] | 291 |
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[559] | 292 | /**
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| 293 | * <p>
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| 294 | * Helper class for graph visualization of a trie.
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| 295 | * </p>
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| 296 | *
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| 297 | * @author Steffen Herbold
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| 298 | * @version 1.0
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| 299 | */
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| 300 | static public class Edge {}
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[518] | 301 |
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[559] | 302 | /**
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| 303 | * <p>
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| 304 | * Helper class for graph visualization of a trie.
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| 305 | * </p>
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| 306 | *
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| 307 | * @author Steffen Herbold
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| 308 | * @version 1.0
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| 309 | */
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| 310 | static public class TrieVertex {
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[518] | 311 |
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[559] | 312 | /**
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| 313 | * <p>
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| 314 | * Id of the vertex.
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| 315 | * </p>
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| 316 | */
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| 317 | private String id;
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[518] | 318 |
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[559] | 319 | /**
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| 320 | * <p>
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| 321 | * Contructor. Creates a new TrieVertex.
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| 322 | * </p>
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| 323 | *
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| 324 | * @param id
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| 325 | * id of the vertex
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| 326 | */
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| 327 | protected TrieVertex(String id) {
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| 328 | this.id = id;
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| 329 | }
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[518] | 330 |
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[559] | 331 | /**
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| 332 | * <p>
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| 333 | * Returns the id of the vertex.
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| 334 | * </p>
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| 335 | *
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| 336 | * @see java.lang.Object#toString()
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| 337 | */
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| 338 | @Override
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| 339 | public String toString() {
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| 340 | return id;
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| 341 | }
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| 342 | }
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[518] | 343 |
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[559] | 344 | /**
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| 345 | * <p>
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| 346 | * Returns a {@link Graph} representation of the trie.
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| 347 | * </p>
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| 348 | *
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| 349 | * @return {@link Graph} representation of the trie
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| 350 | */
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| 351 | protected Tree<TrieVertex, Edge> getGraph() {
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| 352 | DelegateTree<TrieVertex, Edge> graph = new DelegateTree<TrieVertex, Edge>();
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| 353 | rootNode.getGraph(null, graph);
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| 354 | return graph;
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| 355 | }
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[518] | 356 |
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[559] | 357 | /*
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| 358 | * (non-Javadoc)
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| 359 | *
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| 360 | * @see de.ugoe.cs.quest.usageprofiles.IDotCompatible#getDotRepresentation()
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| 361 | */
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| 362 | public String getDotRepresentation() {
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| 363 | StringBuilder stringBuilder = new StringBuilder();
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| 364 | stringBuilder.append("digraph model {" + StringTools.ENDLINE);
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| 365 | rootNode.appendDotRepresentation(stringBuilder);
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| 366 | stringBuilder.append('}' + StringTools.ENDLINE);
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| 367 | return stringBuilder.toString();
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| 368 | }
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[518] | 369 |
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[559] | 370 | /**
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| 371 | * <p>
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| 372 | * Returns the string representation of the root node.
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| 373 | * </p>
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| 374 | *
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| 375 | * @see TrieNode#toString()
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| 376 | * @see java.lang.Object#toString()
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| 377 | */
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| 378 | @Override
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| 379 | public String toString() {
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| 380 | return rootNode.toString();
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| 381 | }
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[518] | 382 |
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[559] | 383 | /**
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| 384 | * <p>
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| 385 | * Returns the number of symbols contained in the trie.
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| 386 | * </p>
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| 387 | *
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| 388 | * @return number of symbols contained in the trie
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| 389 | */
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| 390 | public int getNumSymbols() {
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| 391 | return knownSymbols.size();
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| 392 | }
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[518] | 393 |
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[559] | 394 | /**
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| 395 | * <p>
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| 396 | * Returns the number of trie nodes that are ancestors of a leaf. This is the equivalent to the
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| 397 | * number of states a first-order markov model would have.
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| 398 | * <p>
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| 399 | *
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| 400 | * @return number of trie nodes that are ancestors of leafs.
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| 401 | */
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| 402 | public int getNumLeafAncestors() {
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| 403 | List<TrieNode<T>> ancestors = new LinkedList<TrieNode<T>>();
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| 404 | rootNode.getLeafAncestors(ancestors);
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| 405 | return ancestors.size();
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| 406 | }
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[518] | 407 |
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[559] | 408 | /**
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| 409 | * <p>
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| 410 | * Returns the number of trie nodes that are leafs.
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| 411 | * </p>
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| 412 | *
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| 413 | * @return number of leafs in the trie
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| 414 | */
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| 415 | public int getNumLeafs() {
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| 416 | return rootNode.getNumLeafs();
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| 417 | }
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[518] | 418 |
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[559] | 419 | /**
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| 420 | * <p>
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| 421 | * Updates the list of known symbols by replacing it with all symbols that are found in the
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| 422 | * child nodes of the root node. This should be the same as all symbols that are contained in
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| 423 | * the trie.
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| 424 | * </p>
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| 425 | */
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| 426 | public void updateKnownSymbols() {
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| 427 | knownSymbols = new HashSet<T>();
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| 428 | for (TrieNode<T> node : rootNode.getChildren()) {
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| 429 | knownSymbols.add(node.getSymbol());
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| 430 | }
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| 431 | }
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[518] | 432 |
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[559] | 433 | /**
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| 434 | * <p>
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| 435 | * Two Tries are defined as equal, if their {@link #rootNode} are equal.
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| 436 | * </p>
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| 437 | *
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| 438 | * @see java.lang.Object#equals(java.lang.Object)
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| 439 | */
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| 440 | @SuppressWarnings("rawtypes")
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| 441 | @Override
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| 442 | public boolean equals(Object other) {
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| 443 | if (other == this) {
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| 444 | return true;
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| 445 | }
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| 446 | if (other instanceof Trie) {
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| 447 | return rootNode.equals(((Trie) other).rootNode);
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| 448 | }
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| 449 | return false;
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| 450 | }
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| 451 |
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| 452 | /*
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| 453 | * (non-Javadoc)
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| 454 | *
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| 455 | * @see java.lang.Object#hashCode()
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| 456 | */
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| 457 | @Override
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| 458 | public int hashCode() {
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| 459 | int multiplier = 17;
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| 460 | int hash = 42;
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| 461 | if (rootNode != null) {
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| 462 | hash = multiplier * hash + rootNode.hashCode();
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| 463 | }
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| 464 | return hash;
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| 465 | }
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[518] | 466 | }
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