package com.fox.analyzer;import java.util.ArrayList;
import java.util.List;public class Trie {private Vertex root = new Vertex();protected class Vertex {protected int words; // 单词个数protected int prefixes; // 前缀个数protected Vertex[] edges; // 子节点Vertex() {this.words = 0;this.prefixes = 0;edges = new Vertex[26];for (int i = 0; i < edges.length; i++) {edges[i] = null;}}}/*** 获取tire树中所有的词* * @return*/public List<String> listAllWords() {List<String> words = new ArrayList<String>();Vertex[] edges = root.edges;for (int i = 0; i < edges.length; i++) {if (edges[i] != null) {String word = "" + (char) ('a' + i);depthFirstSearchWords(words, edges[i], word);}}return words;}/*** * @param words* @param vertex* @param wordSegment*/private void depthFirstSearchWords(List words, Vertex vertex,String wordSegment) {if (vertex.words != 0) {words.add(wordSegment);}Vertex[] edges = vertex.edges;for (int i = 0; i < edges.length; i++) {if (edges[i] != null) {String newWord = wordSegment + (char) ('a' + i);depthFirstSearchWords(words, edges[i], newWord);}}}/*** 计算指定前缀单词的个数* * @param prefix* @return*/public int countPrefixes(String prefix) {return countPrefixes(root, prefix);}private int countPrefixes(Vertex vertex, String prefixSegment) {if (prefixSegment.length() == 0) { // reach the last character of the// wordreturn vertex.prefixes;}char c = prefixSegment.charAt(0);int index = c - 'a';if (vertex.edges[index] == null) { // the word does NOT existreturn 0;} else {return countPrefixes(vertex.edges[index],prefixSegment.substring(1));}}/*** 计算完全匹配单词的个数* * @param word* @return*/public int countWords(String word) {return countWords(root, word);}private int countWords(Vertex vertex, String wordSegment) {if (wordSegment.length() == 0) { // reach the last character of the wordreturn vertex.words;}char c = wordSegment.charAt(0);int index = c - 'a';if (vertex.edges[index] == null) { // the word does NOT existreturn 0;} else {return countWords(vertex.edges[index], wordSegment.substring(1));}}/*** 向tire树添加一个词* * @param word* */public void addWord(String word) {addWord(root, word);}/*** Add the word from the specified vertex.* * @param vertex*            The specified vertex.* @param word*            The word to be added.*/private void addWord(Vertex vertex, String word) {if (word.length() == 0) { // if all characters of the word has been// addedvertex.words++;} else {vertex.prefixes++;char c = word.charAt(0);c = Character.toLowerCase(c);int index = c - 'a';if (vertex.edges[index] == null) { // if the edge does NOT existvertex.edges[index] = new Vertex();}addWord(vertex.edges[index], word.substring(1)); // go the the next// character}}/*** 返回指定字段前缀匹配最长的单词。* * @param word* @return*/public String getMaxMatchWord(String word) {String s = "";String temp = "";// 记录最近一次匹配最长的单词char[] w = word.toCharArray();Vertex vertex = root;for (int i = 0; i < w.length; i++) {char c = w[i];c = Character.toLowerCase(c);int index = c - 'a';if (vertex.edges[index] == null) {// 如果没有子节点if (vertex.words != 0)// 如果是一个单词，则返回return s;else// 如果不是一个单词则返回nullreturn null;} else {if (vertex.words != 0)temp = s;s += c;vertex = vertex.edges[index];}}// trie中存在比指定单词更长（包含指定词）的单词if (vertex.words == 0)//return temp;return s;}public static void main(String args[]) // Just used for test{Trie trie = new Trie();trie.addWord("abcedfddddddd");trie.addWord("a");trie.addWord("ba");trie.addWord("abce");trie.addWord("abcedfdddd");trie.addWord("abcef");String maxMatch = trie.getMaxMatchWord("abcedfddd");System.out.println(maxMatch);// List<String> list = trie.listAllWords();// Iterator listiterator = list.listIterator();// while (listiterator.hasNext()) {// String s = (String) listiterator.next();// System.out.println(s);// }// int count = trie.countPrefixes("abcdef");// int count1 = trie.countWords("abcd");// System.out.println("prefixes:" + count);// System.out.println("countWords:" + count1);}
}