1.简介

字典树：也叫做前缀树，是一种高效的存储、配对字符串的数据结构，存储过程如下：

假设我们有单词：app、apple、cat。如果存在链表中：

["app"、"apple"、"api"、"cat"]，要保存14个字符，使用字典树之后就变成了9个字符

2.代码实现

话不多说，代码很简洁，直接看注释就能看懂，如下： 

package 算法;import sun.reflect.generics.tree.Tree;import java.util.Arrays;
import java.util.HashMap;
import java.util.List;
import java.util.Map;/*** @Author: stukk* @Description: 字典树**/
public class TrieTree {private TreeNode root;//    初始化树public TrieTree() {this.root = new TreeNode();}//    添加单词public void addWord(String word) {TreeNode treeNode = root;for (char ch : word.toCharArray()) {if (!treeNode.contains(ch)) {treeNode.addChildren(ch, new TreeNode());}treeNode = treeNode.getChildren(ch);}treeNode.setIsWord(true);}//    查找前缀匹配public TreeNode searchPrefix(String prefix) {TreeNode treeNode = root;for (char ch : prefix.toCharArray()) {if (!treeNode.contains(ch)) {return null;}treeNode = treeNode.getChildren(ch);}return treeNode;}//    查找单词public boolean searchWord(String word) {TreeNode node = searchPrefix(word);return node != null && node.getWord();}//   敏感词过滤 true代表通过过滤public boolean filter(String sentence) {TreeNode treeNode = root;int nowIndex = 0, startIndex = 0;while (startIndex < sentence.length()) {char ch = sentence.charAt(nowIndex);if (treeNode.contains(ch)) {treeNode = treeNode.getChildren(ch);if (treeNode.getWord()) {//是一个违禁词return false;}nowIndex++;} else {startIndex++;nowIndex = startIndex;treeNode = root;}}return true;}public void setWords(List<String> words) {for (String word : words) {addWord(word);}}public static void main(String[] args) {TrieTree trieTree = new TrieTree();trieTree.setWords(Arrays.asList("你大爷"));boolean filter = trieTree.filter("我*你大爷的");if (filter) {System.out.println("不违规");} else {System.out.println("违规");}}}//树的结点
class TreeNode {private Map<Character, TreeNode> children;private Boolean isWord;public TreeNode() {this.children = new HashMap<>();this.isWord = false;}//    是否是这个字符public boolean contains(char ch) {return children.containsKey(ch);}//    添加字符public void addChildren(char ch, TreeNode treeNode) {children.put(ch, treeNode);}public TreeNode getChildren(char ch) {return children.get(ch);}public void setIsWord(boolean ok) {isWord = ok;}public Boolean getWord() {return isWord;}
}