211. 添加与搜索单词 - 数据结构设计

import java.util.TreeMap;

class WordDictionary {

    class Node{

        boolean isWord;
        TreeMap<Character, Node> next;

        public Node(){

            isWord = false;
            next = new TreeMap<>();
        }
    }

    Node root;

    public WordDictionary() {

        root = new Node();
    }

    public void addWord(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;
    }

    public boolean search(String word){

        return match(root, word, 0);
    }

    /**
     * 传入要查找的字典树的根节点root，要查询的字符串word和要查询的字符串的第几个字符index
     * 当index到达末尾时，说明遍历完了，这时只需判断这个节点的isWord是否为真
     * 如果c是.，那么要对该节点所有的子节点进行遍历，只要有一种情况符合就返回true
     * Map类的keySet()方法获取所有的键
     */
    private boolean match(Node root, String word, int index){

        if (word.length() == index){
            return root.isWord;
        }

        char c = word.charAt(index);

        if (c != '.'){

            if (root.next.get(c) == null){
                return false;
            }
            else {
                return match(root.next.get(c), word, index + 1);
            }
        }
        else {

            for (char nextChar : root.next.keySet()){

                if (match(root.next.get(nextChar), word, index + 1)){
                    return true;
                }
            }

            return false;
        }
    }
}

https://leetcode-cn.com/problems/design-add-and-search-words-data-structure/