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TernaryTree
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com.lowagie.text.pdf.hyphenation</FONT>
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Class TernaryTree</H2>
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<A HREF="http://java.sun.com/j2se/1.3/docs/api/java/lang/Object.html">java.lang.Object</A>
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+--<B>com.lowagie.text.pdf.hyphenation.TernaryTree</B>
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<DT><B>All Implemented Interfaces:</B> <DD><A HREF="http://java.sun.com/j2se/1.3/docs/api/java/lang/Cloneable.html">Cloneable</A>, <A HREF="http://java.sun.com/j2se/1.3/docs/api/java/io/Serializable.html">Serializable</A></DD>
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<DT><B>Direct Known Subclasses:</B> <DD><A HREF="../../../../../com/lowagie/text/pdf/hyphenation/HyphenationTree.html">HyphenationTree</A></DD>
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<DT>public class <B>TernaryTree</B><DT>extends <A HREF="http://java.sun.com/j2se/1.3/docs/api/java/lang/Object.html">Object</A><DT>implements <A HREF="http://java.sun.com/j2se/1.3/docs/api/java/lang/Cloneable.html">Cloneable</A>, <A HREF="http://java.sun.com/j2se/1.3/docs/api/java/io/Serializable.html">Serializable</A></DL>
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<h2>Ternary Search Tree</h2> <p>A ternary search tree is a hibrid between a binary tree and a digital search tree (trie). Keys are limited to strings. A data value of type char is stored in each leaf node. It can be used as an index (or pointer) to the data. Branches that only contain one key are compressed to one node by storing a pointer to the trailer substring of the key. This class is intended to serve as base class or helper class to implement Dictionary collections or the like. Ternary trees have some nice properties as the following: the tree can be traversed in sorted order, partial matches (wildcard) can be implemented, retrieval of all keys within a given distance from the target, etc. The storage requirements are higher than a binary tree but a lot less than a trie. Performance is comparable with a hash table, sometimes it outperforms a hash function (most of the time can determine a miss faster than a hash).</p> <p>The main purpose of this java port is to serve as a base for implementing TeX's hyphenation algorithm (see The TeXBook, appendix H). Each language requires from 5000 to 15000 hyphenation patterns which will be keys in this tree. The strings patterns are usually small (from 2 to 5 characters), but each char in the tree is stored in a node. Thus memory usage is the main concern. We will sacrify 'elegance' to keep memory requirenments to the minimum. Using java's char type as pointer (yes, I know pointer it is a forbidden word in java) we can keep the size of the node to be just 8 bytes (3 pointers and the data char). This gives room for about 65000 nodes. In my tests the english patterns took 7694 nodes and the german patterns 10055 nodes, so I think we are safe.</p> <p>All said, this is a map with strings as keys and char as value. Pretty limited!. It can be extended to a general map by using the string representation of an object and using the char value as an index to an array that contains the object values.</p>
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<DT><B>Author:</B><DD>cav@uniscope.co.jp</DD></DD><DT><B>See Also:</B><DD><A HREF="../../../../../serialized-form.html" TARGET="com.lowagie.text.pdf.hyphenation.TernaryTree">Serialized Form</A></DL>
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<CODE> class</CODE></FONT></TD>
<TD><CODE><B><A HREF="../../../../../com/lowagie/text/pdf/hyphenation/TernaryTree.Iterator.html">TernaryTree.Iterator</A></B></CODE>
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<!-- =========== FIELD SUMMARY =========== -->
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<B>Field Summary</B></FONT></TD>
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<CODE>protected static int</CODE></FONT></TD>
<TD><CODE><B><A HREF="../../../../../com/lowagie/text/pdf/hyphenation/TernaryTree.html#BLOCK_SIZE">BLOCK_SIZE</A></B></CODE>
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<CODE>protected char[]</CODE></FONT></TD>
<TD><CODE><B><A HREF="../../../../../com/lowagie/text/pdf/hyphenation/TernaryTree.html#eq">eq</A></B></CODE>
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Pointer to equal branch and to data when this node is a string terminator.</TD>
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<CODE>protected char</CODE></FONT></TD>
<TD><CODE><B><A HREF="../../../../../com/lowagie/text/pdf/hyphenation/TernaryTree.html#freenode">freenode</A></B></CODE>
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<CODE>protected char[]</CODE></FONT></TD>
<TD><CODE><B><A HREF="../../../../../com/lowagie/text/pdf/hyphenation/TernaryTree.html#hi">hi</A></B></CODE>
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Pointer to high branch.</TD>
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<CODE>protected <A HREF="../../../../../com/lowagie/text/pdf/hyphenation/CharVector.html">CharVector</A></CODE></FONT></TD>
<TD><CODE><B><A HREF="../../../../../com/lowagie/text/pdf/hyphenation/TernaryTree.html#kv">kv</A></B></CODE>
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This vector holds the trailing of the keys when the branch is compressed.</TD>
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<CODE>protected int</CODE></FONT></TD>
<TD><CODE><B><A HREF="../../../../../com/lowagie/text/pdf/hyphenation/TernaryTree.html#length">length</A></B></CODE>
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<CODE>protected char[]</CODE></FONT></TD>
<TD><CODE><B><A HREF="../../../../../com/lowagie/text/pdf/hyphenation/TernaryTree.html#lo">lo</A></B></CODE>
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Pointer to low branch and to rest of the key when it is stored directly in this node, we don't have unions in java!</TD>
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<CODE>protected char</CODE></FONT></TD>
<TD><CODE><B><A HREF="../../../../../com/lowagie/text/pdf/hyphenation/TernaryTree.html#root">root</A></B></CODE>
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<CODE>protected char[]</CODE></FONT></TD>
<TD><CODE><B><A HREF="../../../../../com/lowagie/text/pdf/hyphenation/TernaryTree.html#sc">sc</A></B></CODE>
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The character stored in this node: splitchar Two special values are reserved: 0x0000 as string terminator 0xFFFF to indicate that the branch starting at this node is compressed This shouldn't be a problem if we give the usual semantics to strings since 0xFFFF is garanteed not to be an Unicode character.</TD>
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<!-- ======== CONSTRUCTOR SUMMARY ======== -->
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<CODE>(package private)</CODE></FONT></TD>
<TD><CODE><B><A HREF="../../../../../com/lowagie/text/pdf/hyphenation/TernaryTree.html#TernaryTree()">TernaryTree</A></B>()</CODE>
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<CODE> void</CODE></FONT></TD>
<TD><CODE><B><A HREF="../../../../../com/lowagie/text/pdf/hyphenation/TernaryTree.html#balance()">balance</A></B>()</CODE>
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Balance the tree for best search performance</TD>
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<TR BGCOLOR="white" CLASS="TableRowColor">
<TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1">
<CODE> <A HREF="http://java.sun.com/j2se/1.3/docs/api/java/lang/Object.html">Object</A></CODE></FONT></TD>
<TD><CODE><B><A HREF="../../../../../com/lowagie/text/pdf/hyphenation/TernaryTree.html#clone()">clone</A></B>()</CODE>
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<CODE>private void</CODE></FONT></TD>
<TD><CODE><B><A HREF="../../../../../com/lowagie/text/pdf/hyphenation/TernaryTree.html#compact(com.lowagie.text.pdf.hyphenation.CharVector, com.lowagie.text.pdf.hyphenation.TernaryTree, char)">compact</A></B>(<A HREF="../../../../../com/lowagie/text/pdf/hyphenation/CharVector.html">CharVector</A> kx, <A HREF="../../../../../com/lowagie/text/pdf/hyphenation/TernaryTree.html">TernaryTree</A> map, char p)</CODE>
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<CODE> int</CODE></FONT></TD>
<TD><CODE><B><A HREF="../../../../../com/lowagie/text/pdf/hyphenation/TernaryTree.html#find(char[], int)">find</A></B>(char[] key, int start)</CODE>
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<CODE> int</CODE></FONT></TD>
<TD><CODE><B><A HREF="../../../../../com/lowagie/text/pdf/hyphenation/TernaryTree.html#find(java.lang.String)">find</A></B>(<A HREF="http://java.sun.com/j2se/1.3/docs/api/java/lang/String.html">String</A> key)</CODE>
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<TD ALIGN="right" VALIGN="top" WIDTH="1%"><FONT SIZE="-1">
<CODE>protected void</CODE></FONT></TD>
<TD><CODE><B><A HREF="../../../../../com/lowagie/text/pdf/hyphenation/TernaryTree.html#init()">init</A></B>()</CODE>
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<CODE> void</CODE></FONT></TD>
<TD><CODE><B><A HREF="../../../../../com/lowagie/text/pdf/hyphenation/TernaryTree.html#insert(char[], int, char)">insert</A></B>(char[] key, int start, char val)</CODE>
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<CODE>private char</CODE></FONT></TD>
<TD><CODE><B><A HREF="../../../../../com/lowagie/text/pdf/hyphenation/TernaryTree.html#insert(char, char[], int, char)">insert</A></B>(char p, char[] key, int start, char val)</CODE>
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