leetcode-safe trie

trie.py

import collections

class Trie:
    def __init__(self):
        self.children = collections.defaultdict(Trie)
        self.is_leaf = False
    def add(self, string):
        if string == '':
            self.is_leaf = True
        else:
            head = string[0]
            tail = string[1:]
            self.children[head].add(tail)
    def contains(self, string):
        if string == '':
            return self.is_leaf
        else:
            head = string[0]
            tail = string[1:]
            return self.children[head].contains(tail)

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