Trie Basics

import java.util.TreeMap;

public class Trie {

    private class Node{

        public boolean isWord;
        public TreeMap next;

        public Node(boolean isWord){
            this.isWord = isWord;
            next = new TreeMap();
        }

        public Node(){
            this(false);
        }
    }

    private Node root;
    private int size;

    public Trie(){
        root = new Node();
        size = 0;
    }

    // 获得Trie中存储的单词数量
    public int getSize(){
        return size;
    }

    // 向Trie中添加一个新的单词word
    public void add(String word){

        Node cur = root;
        for(int i = 0 ; i 

searchig in trie

    // 查询单词word是否在Trie中
    public boolean contains(String word){

        Node cur = root;
        for(int i = 0 ; i 

前缀查询

   // 查询是否在Trie中有单词以prefix为前缀
    public boolean isPrefix(String prefix){

        Node cur = root;
        for(int i = 0 ; i 

Leetcode208 实现Trie

/// 208. Implement Trie (Prefix Tree)
/// https://leetcode.com/problems/implement-trie-prefix-tree/description/

import java.util.TreeMap;
public class Trie208 {

    private class Node{

        public boolean isWord;
        public TreeMap next;

        public Node(boolean isWord){
            this.isWord = isWord;
            next = new TreeMap();
        }

        public Node(){
            this(false);
        }
    }

    private Node root;

    public Trie208(){
        root = new Node();
    }

    // 向Trie中添加一个新的单词word
    public void insert(String word){

        Node cur = root;
        for(int i = 0 ; i 

Leetcode211 添加与搜索单词

/// Leetcode 211. Add and Search Word - Data structure design
/// https://leetcode.com/problems/add-and-search-word-data-structure-design/description/

import java.util.TreeMap;

public class WordDictionary {

    private class Node{

        public boolean isWord;
        public TreeMap next;

        public Node(boolean isWord){
            this.isWord = isWord;
            next = new TreeMap();
        }

        public Node(){
            this(false);
        }
    }

    private Node root;

    /** Initialize your data structure here. */
    public WordDictionary() {
        root = new Node();
    }

    /** Adds a word into the data structure. */
    public void addWord(String word) {

        Node cur = root;
        for(int i = 0 ; i 

Leetcode 677 Map Sum Pairs

import java.util.TreeMap;

public class MapSum {

    private class Node{

        public int value;
        public TreeMap next;

        public Node(int value){
            this.value = value;
            next = new TreeMap();
        }

        public Node(){
            this(0);
        }
    }

    private Node root;

    /** Initialize your data structure here. */
    public MapSum() {

        root = new Node();
    }

    public void insert(String key, int val) {

        Node cur = root;
        for(int i = 0 ; i 

Trie的删除操作

• 当搜索到该单词的最后一个字母时，自底向上的删除
• 当首字母被公用的时候，保留首字母，只删除后面的字母就行
• 当删除的最后一个字母根本不是叶子节点的时候，直接删除isword就行

Trie局限性