# Add and Search Word - Data structure design（Trie)

Design a data structure that supports the following two operations:

```
void addWord(word)
bool search(word)
```

search(word) can search a literal word or a regular expression string containing only letters`a-z`or`.`. A`.`means it can represent any one letter.

**Example:**

```
addWord("bad")
addWord("dad")
addWord("mad")
search("pad") -> false
search("bad") -> true
search(".ad") -> true
search("b..") -> true
```

**Note:**\
You may assume that all words are consist of lowercase letters`a-z`.

分析

Trie用递归

```
import collections
import string


class TrieNode:
    def __init__(self,c):
        self.c = c
        self.children = collections.defaultdict(TrieNode)
        self.hasWord = False

class WordDictionary:
    LETTERS = list(string.ascii_lowercase)

    def __init__(self):
        """
        Initialize your data structure here.
        """
        self.trie = TrieNode('')


    def addWord(self, word):
        """
        Adds a word into the data structure.
        :type word: str
        :rtype: void
        """
        self.insert(self.trie,word,0)

    def insert(self,trieNode,word,pos):
        if pos == len(word):
            trieNode.hasWord = True
            return
        if word[pos] != '.':
            if word[pos] not in trieNode.children:
                trieNode.children[word[pos]] = TrieNode(word[pos])
            self.insert(trieNode.children.get(word[pos]),word,pos+1)
        else:
            for c in self.LETTERS:
                if c not in trieNode.children:
                    trieNode.children[c] = TrieNode(c)
                self.insert(trieNode.children.get(c), word, pos + 1)


    def search(self, word):
        """
        Returns if the word is in the data structure. A word could contain the dot character '.' to represent any one letter.
        :type word: str
        :rtype: bool
        """
        return self.exist(self.trie,word,0)

    def exist(self, trieNode, word, pos):
        if pos == len(word):
            return trieNode.hasWord

        if word[pos] != '.':
            return word[pos] in trieNode.children and self.exist(trieNode.children.get(word[pos]), word, pos + 1)
        else:
            res = False
            for c in self.LETTERS:
                if c in trieNode.children and self.exist(trieNode.children.get(c), word, pos + 1):
                    res = True
                    break
        return res


# Your WordDictionary object will be instantiated and called as such:
# obj = WordDictionary()
# obj.addWord(word)
# param_2 = obj.search(word)
```

忘了Insert不必考虑.的情况

```
import collections
import string


class TrieNode:
    def __init__(self, c):
        self.c = c
        self.children = collections.defaultdict(TrieNode)
        self.hasWord = False


class WordDictionary:
    LETTERS = list(string.ascii_lowercase)

    def __init__(self):
        """
        Initialize your data structure here.
        """
        self.trie = TrieNode('')

    def addWord(self, word):
        """
        Adds a word into the data structure.
        :type word: str
        :rtype: void
        """
        cur = self.trie
        for c in word:
            if c not in cur.children:
                cur.children[c] = TrieNode(c)
            cur = cur.children.get(c)
        cur.hasWord = True

        # self.insert(self.trie, word, 0)

    def insert(self, trieNode, word, pos):
        if pos == len(word):
            trieNode.hasWord = True
            return
        if word[pos] != '.':
            if word[pos] not in trieNode.children:
                trieNode.children[word[pos]] = TrieNode(word[pos])
            self.insert(trieNode.children.get(word[pos]), word, pos + 1)
        else:
            for c in self.LETTERS:
                if c not in trieNode.children:
                    trieNode.children[c] = TrieNode(c)
                self.insert(trieNode.children.get(c), word, pos + 1)

    def search(self, word):
        """
        Returns if the word is in the data structure. A word could contain the dot character '.' to represent any one letter.
        :type word: str
        :rtype: bool
        """
        return self.exist(self.trie, word, 0)

    def exist(self, trieNode, word, pos):
        if pos == len(word):
            return trieNode.hasWord

        if word[pos] != '.':
            return word[pos] in trieNode.children and self.exist(trieNode.children.get(word[pos]), word, pos + 1)
        else:
            res = False
            for c in self.LETTERS:
                if c in trieNode.children and self.exist(trieNode.children.get(c), word, pos + 1):
                    res = True
                    break
        return res

# Your WordDictionary object will be instantiated and called as such:
# obj = WordDictionary()
# obj.addWord(word)
# param_2 = obj.search(word)
```


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