Question

我需要一些帮助才能完成此代码。我不指望你给我完整的答案，我只需要一些关于2个功能的提示。感谢

class Trie(object):
    """A Trie of TrieNodes. Trie has the following attributes:
     -- _root: a TrieNode; the root of this Trie.
    """

    def __init__(self):
        """Create an empty Trie."""

        self._root = TrieNode()

    def insert(self, word, data):
        """Insert the string 'word' with data 'data' into this Trie.

        -- word: the string with which the newly inserted 'data' will
           be associated.
        -- data: the data which will be stored in the TrieNode
           associated with the string 'word'.

        If there is a TrieNode associated with the word 'word' in this
        Trie, then _data of this TrieNode is updated to 'data'. Otherwise,
        enough new TrieNodes are created and inserted into this Trie, to
        create a TrieNode associated with 'word'.
        """

        raise Exception, "Implement me!"

    def find_node(self, word):
        """Return the TrieNode that corresponds to the string 'word'
        in this Trie. Return None if there is no such TrieNode in this
        Trie.
        -- word: a string; the TrieNode that corresponds to 'word'
        (if it exists) is returned.
        """

        raise Exception, "Implement me!"

Answer 1

如果您想要的只是一个提示，请查看Wikipedia's entry for the trie，它会告诉您有关尝试如何工作的所有信息。

好的，这是另一个提示：trie的每个节点都包含一个字典，其键是字符，其值是trie节点。 insert方法将查看word[0]，查找或创建该字符的节点，然后，如果len(word)大于1，则使用word[1:]执行某些操作。

Answer 2

如果罗伯特的提示还不够，这里有一个Trie的最小实现，其中包含您遇到问题的两个函数。

class Trie(object):
    def __init__(self, char='', data=None):
        self.children = []
        self.char = char
        self.data = data

    def get_child(self, char):
        for child in self.children:
            if child.char == char:
                return child

    def insert(self, key, data, node=None):
        if node is None:
            node = self
        if len(key) == 0:
            #key found
            node.data = data
            return node.data
        else:
            child = node.get_child(key[0])
            if child is None:
                child = Trie(key[0])
                node.children.append(child)
                return self.insert(key[1:], data, child)
            return self.insert(key[1:], data, child)

    def find(self, key, node=None):
        if node is None:
            node = self
        if len(key) == 0:
            #key found
            return node.data
        else:
            child = node.get_child(key[0])

            if child is None:
                return None
            return self.find(key[1:], child)

>>> tree = Trie()
>>> tree.insert('t', 't data')
>>> tree.insert('tr', 'tr data')
>>> print tree.find('t'), tree.find('tr')
t data tr data

需要帮助完成一个程序

2 个答案: