［leetcode刷题笔记］Implement Trie (Prefix Tree)

题目链接

一A，开森～

ac代码：

class TrieNode {
    // Initialize your data structure here.
    char content;
    boolean isWord;
    int count;
    LinkedList<TrieNode> childList;
    
    public TrieNode(char c) {
        content = c;
        isWord = false;
        count = 0;
        childList = new LinkedList<TrieNode>();
    }
    public TrieNode() {
        content = ' ';
        isWord = false;
        count = 0;
        childList = new LinkedList<TrieNode>();
    }
    
    public TrieNode findChildC(char c){
        if(childList != null){
            for(TrieNode eachChild:childList){
                if(eachChild.content == c)
                    return eachChild;
            }
        }
        return null;
    }
}

public class Trie {
    private TrieNode root;

    public Trie() {
        root = new TrieNode();
        
    }

    // Inserts a word into the trie.
    public void insert(String word) {
        //if already has this word
        if(search(word) == true)
            return;
        
        TrieNode current = root;
        for(int i = 0;i < word.length();i++){
            TrieNode child = current.findChildC(word.charAt(i));
            if(child == null){
                TrieNode temp = new TrieNode(word.charAt(i));
                current.childList.add(temp);
                current = temp;
            }else{
                current = child;
            }
            current.count++;
        }
        current.isWord = true;
    }

    // Returns if the word is in the trie.
    public boolean search(String word) {
        TrieNode current = root;
        for(int i = 0;i < word.length();i++){
            TrieNode child = current.findChildC(word.charAt(i));
            if(child == null)
                return false;
            else{
                current = child;
                continue;
            }
        }
        if(current.isWord)
            return true;
        return false;
    }

    // Returns if there is any word in the trie
    // that starts with the given prefix.
    public boolean startsWith(String prefix) {
        TrieNode current = root;
        for(int i = 0;i < prefix.length();i++){
            TrieNode child = current.findChildC(prefix.charAt(i));
            if(child == null)
                return false;
            else{
                current = child;
                continue;
            }
        }
        return true;
    }
}

// Your Trie object will be instantiated and called as such:
// Trie trie = new Trie();
// trie.insert("somestring");
// trie.search("key");