473.Add and Search Word-单词的添加与查找（中等题）

单词的添加与查找

1. 题目

   设计一个包含下面两个操作的数据结构：addWord(word), search(word)
   addWord(word)会在数据结构中添加一个单词。而search(word)则支持普通的单词查询或是只包含.和a-z的简易正则表达式的查询。
   一个 . 可以代表一个任何的字母。

   注意事项
   你可以假设所有的单词都只包含小写字母 a-z。

2. 样例

   addWord(“bad”)
   addWord(“dad”)
   addWord(“mad”)
   search(“pad”) // return false
   search(“bad”) // return true
   search(“.ad”) // return true
   search(“b..”) // return true

3. 题解

   参看442.Implement Trie-实现 Trie（中等题），只需额外处理一下通配符的问题。

class TrieNode 
{
    private TrieNode[] children;
    public boolean hasWord;

    // Initialize your data structure here.
    public TrieNode() 
    {
        children = new TrieNode[26];
        hasWord = false;
    }

    public void insert(String word, int index) 
    {
        if (index == word.length()) 
        {
            this.hasWord = true;
            return;
        }

        int pos = word.charAt(index) - 'a';
        if (children[pos] == null) 
        {
            children[pos] = new TrieNode();
        }
        children[pos].insert(word, index + 1);
    }

    public boolean find(String word, int index) 
    {
        if (index == word.length()) 
        {
            return this.hasWord;
        }
        if (word.charAt(index) == '.')
        {
            boolean res = false;
            for (int i=0;iif (children[i] != null)
                {
                    res = children[i].find(word, index + 1);
                }
            }
            return res;
        }
        else
        {
            int pos = word.charAt(index) - 'a';
            return children[pos] == null ? false : children[pos].find(word, index + 1);
        }
    }
}

public class WordDictionary {
    private TrieNode root;

    WordDictionary()
    {
        root = new TrieNode();
    }

    // Adds a word into the data structure.
    public void addWord(String word) {
        root.insert(word,0);
    }

    // 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 root.find(word, 0);
    }
}

// Your WordDictionary object will be instantiated and called as such:
// WordDictionary wordDictionary = new WordDictionary();
// wordDictionary.addWord("word");
// wordDictionary.search("pattern");

Last Update 2016.11.18