net.automatalib.util.tries.SuffixTrieNode Maven / Gradle / Ivy
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This artifact provides various common utility operations for analyzing and manipulating
automata and graphs, such as traversal, minimization and copying.
/* Copyright (C) 2013 TU Dortmund
* This file is part of AutomataLib, http://www.automatalib.net/.
*
* AutomataLib is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License version 3.0 as published by the Free Software Foundation.
*
* AutomataLib is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with AutomataLib; if not, see
* http://www.gnu.de/documents/lgpl.en.html.
*/
package net.automatalib.util.tries;
import java.util.List;
import java.util.NoSuchElementException;
import net.automatalib.words.Word;
import net.automatalib.words.WordBuilder;
/**
* A node in a {@link SuffixTrie}.
*
* @author Malte Isberner
*
* @param symbol class.
*/
public class SuffixTrieNode extends Word {
/**
* Optimized iterator for the implicit word representation.
*
* @author Malte Isberner
*
* @param symbol class
*/
private static final class Iterator implements java.util.Iterator {
private SuffixTrieNode current;
public Iterator(SuffixTrieNode node) {
this.current = node;
}
/*
* (non-Javadoc)
* @see java.util.Iterator#hasNext()
*/
@Override
public boolean hasNext() {
return !current.isRoot();
}
/*
* (non-Javadoc)
* @see java.util.Iterator#next()
*/
@Override
public I next() {
if(current.isRoot()) {
throw new NoSuchElementException();
}
I sym = current.symbol;
current = current.parent;
return sym;
}
/*
* (non-Javadoc)
* @see java.util.Iterator#remove()
*/
@Override
public void remove() {
throw new UnsupportedOperationException();
}
}
public static void appendSuffix(SuffixTrieNode node, List symList) {
while(node.parent != null) {
symList.add(node.symbol);
node = node.parent;
}
}
public static Word toExplicitWord(SuffixTrieNode node) {
WordBuilder wb = new WordBuilder(node.depth());
appendSuffix(node, wb);
return wb.toWord();
}
public static int depth(SuffixTrieNode node) {
int d = 0;
while(node.parent != null) {
d++;
node = node.parent;
}
return d;
}
public static I getSymbol(SuffixTrieNode node, int index) {
while(index-- > 0)
node = node.parent;
return node.symbol;
}
private final I symbol;
private final SuffixTrieNode parent;
/**
* Root constructor.
*/
public SuffixTrieNode() {
this.symbol = null;
this.parent = null;
}
public SuffixTrieNode(I symbol, SuffixTrieNode parent) {
this.symbol = symbol;
this.parent = parent;
}
// TODO: replace by getter/attribute?
public int depth() {
return depth(this);
}
public I getSymbol() {
return symbol;
}
public SuffixTrieNode getParent() {
return parent;
}
public boolean isRoot() {
return (parent == null);
}
public void appendSuffix(List symList) {
appendSuffix(this, symList);
}
public Word getSuffix() {
if(parent == null)
return Word.epsilon();
WordBuilder wb = new WordBuilder<>(depth());
appendSuffix(wb);
return wb.toWord();
}
@Override
public I getSymbol(int index) {
return getSymbol(this, index);
}
@Override
public int length() {
return depth();
}
@Override
public Iterator iterator() {
return new Iterator(this);
}
}