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A Java implementation of a Double Array Trie
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Copyright 2010 Christos Gioran This file is part of DoubleArrayTrie. DoubleArrayTrie is free software: you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version. DoubleArrayTrie 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 DoubleArrayTrie. If not, see <http://www.gnu.org/licenses/>. ========================================================================= DoubleArrayTrie is a pure Java implementation of a double array trie. This is a radix tree implemented using two arrays to store the transition diagram instead of pointers/nodes. It is slower for insertions that the graph implementation but is blazingly fast for retrieval. There are 4 parts to this project. One is the implementation of the algorithm itself found in AbstractDoubleArrayTrie. Extending that is DoubleArrayTrieImpl that implements the storage management using two ArrayLists - this is done so that additional storage schemes can be used, such as an odd/even index single array. The second is examples consisting of a CountTrie that simply implements the calls from AbstractDoubleArrayTrie to count insertions and searches. This, along with the test cases provide usage examples (documentation is currently limited to the above, the source and the javadocs). The third is a barebones implementation of a resizing array of integers, because the java core libraries do not provide collections for primitive values and the overhead from the wrapper classes is prohibitive. These are found in org.digitalstain.datrie.store The forth and final part is a preeliminary attempt to provide a wrapper for the common use case of a trie, i.e. storing strings. It shows succinctly but correctly the assumptions that underlie the operation of AbstractDoubleArrayTrie and a way to map string using it. Most of the above will soon be uploaded as a separate documentation project. In order to create useful extentions of the core structure, you must first understand how it works so that you can correctly consume the events of the movement of states around the backing storage. A very good discription is at http://linux.thai.net/~thep/datrie/datrie.html from Theppitak Karoonboonyanan, who also provides libdatrie, a C implementation of the same.