211. 添加与搜索单词 - 数据结构设计

import java.util.HashMap;

public class WordDictionary {

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

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

        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) {
        addWord(root, word, 0);
    }

    private void addWord(Node node, String word, int index) {

        if (word.length() == index) {
            if (!node.isWord) {
                node.isWord = true;
            }
            return;
        }

        char c = word.charAt(index);
        if (node.next.get(c) == null) {
            node.next.put(c, new Node());
        }

        addWord(node.next.get(c), word, index + 1);
    }

    /** Returns if the word is in the data structure. A word could contain the dot character '.' to represent any one letter. */
    public boolean search(String word) {
        return search(root, word, 0);
    }

    private boolean search(Node node, String word, int index) {
        if (word.length() == index) {
            return node.isWord;
        }

        char c = word.charAt(index);
        if (c != '.') {
            if (node.next.get(c) == null) {
                return false;
            }
            return search(node.next.get(c), word, index + 1);
        } else {
            for (Character character : node.next.keySet()) {
                if (search(node.next.get(character), word, index + 1)) {
                    return true;
                }
            }
            return false;
        }
    }
}

/**
 * Your WordDictionary object will be instantiated and called as such:
 * WordDictionary obj = new WordDictionary();
 * obj.addWord(word);
 * boolean param_2 = obj.search(word);
 */