package leetcode_1To300;

/**
 * 本代码来自 Cspiration，由 @Cspiration 提供
 * 题目来源：http://leetcode.com
 * - Cspiration 致力于在 CS 领域内帮助中国人找到工作，让更多海外国人受益
 * - 现有课程：Leetcode Java 版本视频讲解（1-900题）（上）（中）（下）三部
 * - 算法基础知识（上）（下）两部；题型技巧讲解（上）（下）两部
 * - 节省刷题时间，效率提高2-3倍，初学者轻松一天10题，入门者轻松一天20题
 * - 讲师：Edward Shi
 * - 官方网站：https://cspiration.com
 * - 版权所有，转发请注明出处
 */
public class _208_ImplementTrie {

    /**
     * 208. Implement Trie (Prefix Tree)
     */

    TrieNode root;

    /** Initialize your data structure here. */
    public _208_ImplementTrie() {
        root = new TrieNode();
    }

    // time : O(n)  n: word.length();
    // O(num of TrieNode * 26) = O(num of Words * word.length() * 26)
    /** Inserts a word into the trie. */
    public void insert(String word) {
        TrieNode node = root;
        for (int i = 0; i < word.length(); i++) {
            int j = word.charAt(i) - 'a';
            if (node.children[j] == null) {
                node.children[j] = new TrieNode();
            }
            node = node.children[j];
        }
        node.isWord = true;
    }

    /** Returns if the word is in the trie. */
    public boolean search(String word) {
        TrieNode node = root;
        for (int i = 0; i < word.length(); i++) {
            int j = word.charAt(i) - 'a';
            if (node.children[j] == null) return false;
            node = node.children[j];
        }
        return node.isWord;
    }

    /** Returns if there is any word in the trie that starts with the given prefix. */
    public boolean startsWith(String prefix) {
        TrieNode node = root;
        for (int i = 0; i < prefix.length(); i++) {
            int j = prefix.charAt(i) - 'a';
            if (node.children[j] == null) return false;
            node = node.children[j];
        }
        return true;
    }
}