[Java101] Trie Implementation

 

LeetCode: 208. Implement Trie (Prefix Tree)

class TrieNode {
    public boolean isWord = false;
    public TrieNode[] children = new TrieNode[26];
}

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

    public void insert(String word) {
        TrieNode cur = root;
        for (int i=0; i<word.length(); i++) {
            char c = word.charAt(i);
            if (cur.children[c - 'a'] == null) cur.children[c - 'a'] = new TrieNode();
            cur = cur.children[c - 'a'];
        }
        cur.isWord = true;
    }

    public boolean search(String word) {
        TrieNode cur = root;
        for (int i=0; i<word.length(); i++) {
            char c = word.charAt(i);
            if (cur.children[c - 'a'] == null) return false;
            cur = cur.children[c - 'a'];
        }
        return cur.isWord;
    }

    public boolean startsWith(String prefix) {
        TrieNode cur = root;
        for (int i=0; i<prefix.length(); i++) {
            char c = prefix.charAt(i);
            if (cur.children[c - 'a'] == null) return false;
            cur = cur.children[c - 'a'];
        }
        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);
 */