1032. Stream of Characters

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Implement the StreamChecker class as follows:

• StreamChecker(words): Constructor, init the data structure with the given words.
• query(letter): returns true if and only if for some k >= 1, the last k characters queried (in order from oldest to newest, including this letter just queried) spell one of the words in the given list.

Example:

StreamChecker streamChecker = new StreamChecker(["cd","f","kl"]); // init the dictionary.
streamChecker.query('a');          // return false
streamChecker.query('b');          // return false
streamChecker.query('c');          // return false
streamChecker.query('d');          // return true, because 'cd' is in the wordlist
streamChecker.query('e');          // return false
streamChecker.query('f');          // return true, because 'f' is in the wordlist
streamChecker.query('g');          // return false
streamChecker.query('h');          // return false
streamChecker.query('i');          // return false
streamChecker.query('j');          // return false
streamChecker.query('k');          // return false
streamChecker.query('l');          // return true, because 'kl' is in the wordlist

Note:

• 1 <= words.length <= 2000
• 1 <= words[i].length <= 2000
• Words will only consist of lowercase English letters.
• Queries will only consist of lowercase English letters.
• The number of queries is at most 40000.

思路：Trie数，每次query后维护当前还activate的trie node

from collections import defaultdict
Trie = lambda: defaultdict(Trie)

class StreamChecker(object):

    def __init__(self, words):
        """
        :type words: List[str]
        """
        self.trie = Trie()
        for word in words:
            cur = self.trie
            for w in word:
                cur = cur[w]
            cur['END'] = True
        
        self.trie_nodes = [self.trie]
        

    def query(self, letter):
        """
        :type letter: str
        :rtype: bool
        """
        tmp = self.trie_nodes
        self.trie_nodes = [self.trie]
        flag = False
        for node in tmp:
            if letter not in node: continue
            self.trie_nodes.append(node[letter])
            if 'END' in node[letter]: 
                flag = True
        return flag
        


# Your StreamChecker object will be instantiated and called as such:
# obj = StreamChecker(words)
# param_1 = obj.query(letter)