LeetCode208. 实现 Trie (前缀树)（相关话题：字典树，前缀树）

Posted 2020-11-28 不学无墅_NKer

import java.util.TreeMap;
class Trie {

    private class Node{
        public boolean isWord;
        public TreeMap<Character, Node> next;

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

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

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

    }
    
    /** Inserts a word into the trie. */
    public void insert(String word) {
        Node cur = root;
        for(int i = 0; i < word.length(); i++){
            char c = word.charAt(i);
            if(cur.next.get(c) == null){
                cur.next.put(c, new Node());
            }
            cur = cur.next.get(c);
        }
        cur.isWord = true;

    }
    
    /** Returns if the word is in the trie. */
    public boolean search(String word) {

        Node cur = root;
        for(int i = 0 ; i < word.length(); i++){
            char c = word.charAt(i);
            if(cur.next.get(c) == null){
                return false;
            }
            cur = cur.next.get(c);
        }
        return cur.isWord;

    }
    
    /** Returns if there is any word in the trie that starts with the given prefix. */
    public boolean startsWith(String prefix) {
        Node cur = root;
        for(int i = 0; i < prefix.length(); i++){
            char c = prefix.charAt(i);
            if(cur.next.get(c) == null){
                return false;
            }
            cur = cur.next.get(c);
        }
        return true;

    }
}

/**
 * Your Trie object will be instantiated and called as such:
 * Trie obj = new Trie();
 * obj.insert(word);
 * boolean param_2 = obj.search(word);
 * boolean param_3 = obj.startsWith(prefix);
 */

Solution 1

 

Solution 2 （比使用TreeMap时间效率高）： 【40讲系列10】字典树