[13] | 1 | package de.ugoe.cs.eventbench.models;
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[1] | 2 |
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[86] | 3 | import java.io.Serializable;
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[1] | 4 | import java.security.InvalidParameterException;
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[102] | 5 | import java.util.Collection;
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[1] | 6 | import java.util.LinkedList;
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| 7 | import java.util.List;
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| 8 |
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[13] | 9 | import de.ugoe.cs.eventbench.models.Trie.Edge;
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| 10 | import de.ugoe.cs.eventbench.models.Trie.TrieVertex;
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[1] | 11 | import de.ugoe.cs.util.StringTools;
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[5] | 12 | import edu.uci.ics.jung.graph.DelegateTree;
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[106] | 13 | import edu.uci.ics.jung.graph.Tree;
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[1] | 14 |
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[106] | 15 | /**
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| 16 | * <p>
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| 17 | * This class implements a node of a trie. Each node is associated with a symbol
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| 18 | * and has a counter. The counter marks the number of occurences of the sequence
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| 19 | * defined by the path from the root of the trie to this node.
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| 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 | * @see Trie
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| 27 | */
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| 28 | class TrieNode<T> implements Serializable {
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[1] | 29 |
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[86] | 30 | /**
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[106] | 31 | * <p>
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[86] | 32 | * Id for object serialization.
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[106] | 33 | * </p>
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[86] | 34 | */
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| 35 | private static final long serialVersionUID = 1L;
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[106] | 36 |
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| 37 | /**
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| 38 | * <p>
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| 39 | * Counter for the number of occurences of the sequence.
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| 40 | * </p>
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| 41 | */
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[1] | 42 | private int count;
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[106] | 43 |
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| 44 | /**
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| 45 | * <p>
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| 46 | * Symbol associated with the node.
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| 47 | * </p>
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| 48 | */
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[1] | 49 | private final T symbol;
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[106] | 50 |
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| 51 | /**
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| 52 | * <p>
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| 53 | * Child nodes of this node. If the node is a leaf this collection is empty.
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| 54 | * </p>
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| 55 | */
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[102] | 56 | private Collection<TrieNode<T>> children;
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[106] | 57 |
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| 58 | /**
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| 59 | * <p>
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| 60 | * Constructor. Creates a new TrieNode without a symbol associated.<br>
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| 61 | * <b>This constructor should only be used to create the root node of the
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| 62 | * trie!</b>
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| 63 | * </p>
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| 64 | */
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[6] | 65 | TrieNode() {
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| 66 | this.symbol = null;
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| 67 | count = 0;
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| 68 | children = new LinkedList<TrieNode<T>>();
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| 69 | }
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[106] | 70 |
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| 71 | /**
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| 72 | * <p>
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| 73 | * Constructor. Creates a new TrieNode. The symbol must not be null.
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| 74 | * </p>
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| 75 | *
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| 76 | * @param symbol
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| 77 | * symbol associated with the trie node
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| 78 | */
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[1] | 79 | public TrieNode(T symbol) {
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[106] | 80 | if (symbol == null) {
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| 81 | throw new InvalidParameterException(
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| 82 | "symbol must not be null. null is reserved for root node!");
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[1] | 83 | }
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| 84 | this.symbol = symbol;
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| 85 | count = 0;
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| 86 | children = new LinkedList<TrieNode<T>>();
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| 87 | }
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| 88 |
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[106] | 89 | /**
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| 90 | * <p>
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| 91 | * Adds a given subsequence to the trie and increases the counters
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| 92 | * accordingly.
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| 93 | * </p>
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| 94 | *
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| 95 | * @param subsequence
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| 96 | * subsequence whose counters are increased
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| 97 | * @see Trie#add(List)
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| 98 | */
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[1] | 99 | public void add(List<T> subsequence) {
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[106] | 100 | if (!subsequence.isEmpty()) {
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| 101 | if (!symbol.equals(subsequence.get(0))) { // should be guaranteed by
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| 102 | // the
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| 103 | // recursion/TrieRoot!
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[1] | 104 | throw new AssertionError("Invalid trie operation!");
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| 105 | }
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| 106 | count++;
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| 107 | subsequence.remove(0);
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[106] | 108 | if (!subsequence.isEmpty()) {
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[1] | 109 | T nextSymbol = subsequence.get(0);
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| 110 | getChildCreate(nextSymbol).add(subsequence);
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| 111 | }
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| 112 | }
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| 113 | }
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[106] | 114 |
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| 115 | /**
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| 116 | * <p>
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| 117 | * Returns the symbol associated with the node.
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| 118 | * </p>
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| 119 | *
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| 120 | * @return symbol associated with the node
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| 121 | */
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[1] | 122 | public T getSymbol() {
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| 123 | return symbol;
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| 124 | }
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[106] | 125 |
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| 126 | /**
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| 127 | * <p>
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| 128 | * Returns the number of occurences of the sequence represented by the node.
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| 129 | * </p>
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| 130 | *
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| 131 | * @return number of occurences of the sequence represented by the node
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| 132 | */
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[1] | 133 | public int getCount() {
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| 134 | return count;
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| 135 | }
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[106] | 136 |
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| 137 | /**
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| 138 | * <p>
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| 139 | * Returns the child of the node associated with the given symbol or creates
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| 140 | * it if it does not exist yet.
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| 141 | * </p>
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| 142 | *
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| 143 | * @param symbol
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| 144 | * symbol whose node is required
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| 145 | * @return node associated with the symbol
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| 146 | * @see Trie#getChildCreate(Object)
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| 147 | */
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| 148 | protected TrieNode<T> getChildCreate(T symbol) {
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[1] | 149 | TrieNode<T> node = getChild(symbol);
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[106] | 150 | if (node == null) {
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[1] | 151 | node = new TrieNode<T>(symbol);
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| 152 | children.add(node);
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| 153 | }
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| 154 | return node;
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| 155 | }
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[106] | 156 |
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| 157 | /**
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| 158 | * <p>
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| 159 | * Returns the child of the node associated with the given symbol or null if
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| 160 | * it does not exist.
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| 161 | * </p>
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| 162 | *
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| 163 | * @param symbol
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| 164 | * symbol whose node is required
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| 165 | * @return node associated with the symbol; null if no such node exists
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| 166 | * @see Trie#getChild(Object)
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| 167 | */
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[1] | 168 | protected TrieNode<T> getChild(T symbol) {
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[106] | 169 | for (TrieNode<T> child : children) {
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| 170 | if (child.getSymbol().equals(symbol)) {
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[1] | 171 | return child;
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| 172 | }
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| 173 | }
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| 174 | return null;
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| 175 | }
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| 176 |
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[106] | 177 | /**
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| 178 | * <p>
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| 179 | * Searches the sub-trie of this trie node for a given sequence and returns
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| 180 | * the node associated with the sequence or null if no such node is found.
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| 181 | * </p>
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| 182 | *
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| 183 | * @param sequence
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| 184 | * sequence that is searched for
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| 185 | * @return node associated with the sequence
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| 186 | * @see Trie#find(List)
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| 187 | */
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[1] | 188 | public TrieNode<T> find(List<T> subsequence) {
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| 189 | TrieNode<T> result = null;
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[106] | 190 | if (subsequence.isEmpty()) {
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[1] | 191 | result = this;
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| 192 | } else {
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| 193 | TrieNode<T> node = getChild(subsequence.get(0));
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[106] | 194 | if (node != null) {
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[1] | 195 | subsequence.remove(0);
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| 196 | result = node.find(subsequence);
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| 197 | }
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| 198 | }
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| 199 | return result;
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| 200 | }
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[106] | 201 |
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| 202 | /**
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| 203 | * <p>
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| 204 | * Returns a collection of all symbols that follow a this node, i.e., the
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| 205 | * symbols associated with the children of this node.
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| 206 | * </p>
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| 207 | *
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| 208 | * @return symbols follow this node
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| 209 | * @see TrieNode#getFollowingSymbols()
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| 210 | */
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[102] | 211 | public Collection<T> getFollowingSymbols() {
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| 212 | Collection<T> followingSymbols = new LinkedList<T>();
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[106] | 213 | for (TrieNode<T> child : children) {
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[1] | 214 | followingSymbols.add(child.getSymbol());
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| 215 | }
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| 216 | return followingSymbols;
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| 217 | }
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[106] | 218 |
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| 219 | /**
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| 220 | * <p>
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| 221 | * The string representation of a node is {@code symbol.toString()#count}
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| 222 | * </p>
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| 223 | *
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| 224 | * @see java.lang.Object#toString()
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| 225 | */
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[1] | 226 | @Override
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| 227 | public String toString() {
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[106] | 228 | String str = symbol.toString() + " #" + count;
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| 229 | if (!children.isEmpty()) {
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[1] | 230 | str += StringTools.ENDLINE + children.toString();
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| 231 | }
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[106] | 232 | return str;
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[1] | 233 | }
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| 234 |
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[106] | 235 | /**
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| 236 | * <p>
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| 237 | * Generates a {@link Tree} represenation of the trie.
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| 238 | * </p>
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| 239 | *
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| 240 | * @param parent
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| 241 | * parent vertex in the generated tree
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| 242 | * @param graph
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| 243 | * complete tree
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| 244 | */
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| 245 | void getGraph(TrieVertex parent, DelegateTree<TrieVertex, Edge> graph) {
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[6] | 246 | TrieVertex currentVertex;
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[106] | 247 | if (symbol == null) {
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[6] | 248 | currentVertex = new TrieVertex("root");
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| 249 | graph.addVertex(currentVertex);
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| 250 | } else {
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[106] | 251 | currentVertex = new TrieVertex(getSymbol().toString() + "#"
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| 252 | + getCount());
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| 253 | graph.addChild(new Edge(), parent, currentVertex);
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[6] | 254 | }
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[106] | 255 | for (TrieNode<T> node : children) {
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[6] | 256 | node.getGraph(currentVertex, graph);
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[106] | 257 | }
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[5] | 258 | }
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[106] | 259 |
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| 260 | /**
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| 261 | * <p>
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| 262 | * Appends the current node to the dot representation of the trie.
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| 263 | * </p>
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| 264 | *
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| 265 | * @param stringBuilder
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| 266 | * {@link StringBuilder} to which the dot representation is
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| 267 | * appended
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| 268 | */
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[30] | 269 | void appendDotRepresentation(StringBuilder stringBuilder) {
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| 270 | String thisSaneId;
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[106] | 271 | if (symbol == null) {
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[30] | 272 | thisSaneId = "root";
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| 273 | } else {
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[106] | 274 | thisSaneId = symbol.toString().replace("\"", "\\\"")
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| 275 | .replaceAll("[\r\n]", "")
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| 276 | + "#" + count;
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[30] | 277 | }
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[106] | 278 | stringBuilder.append(" " + hashCode() + " [label=\"" + thisSaneId
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| 279 | + "\"];" + StringTools.ENDLINE);
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| 280 | for (TrieNode<T> childNode : children) {
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| 281 | stringBuilder.append(" " + hashCode() + " -> "
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| 282 | + childNode.hashCode() + ";" + StringTools.ENDLINE);
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[30] | 283 | }
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[106] | 284 | for (TrieNode<T> childNode : children) {
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[30] | 285 | childNode.appendDotRepresentation(stringBuilder);
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| 286 | }
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| 287 | }
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[1] | 288 | }
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