[一起来刷leetcode吧][14]--No.208 Trie( Prefix Tree)

最新推荐文章于 2024-03-22 00:51:13 发布

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最新推荐文章于 2024-03-22 00:51:13 发布

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分类专栏： leetcode 一起来刷leetcode吧文章标签： python leetcode os

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本文针对LeetCode上的第208题Trie（前缀树）进行了详细的解答，介绍了Trie的基本概念、实现原理及如何通过Python代码实现Trie的数据结构。包括insert、search和startsWith三个核心方法的具体实现。

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这是leetcode的第208题--Trie( Prefix Tree)

题目 Implement a trie with insert, search, and startsWith methods 思路 trie还是很有趣的，最开始我没弄清楚，以为a->b 再插入abc是

b / a->b->c

正确的应该在每个节点设一个ISKEY 来判断当前前缀是否是存储的一个str。最开始我用的列表来存children，也不好，用字典来存，函数实现就更简洁，而且访问效率高。代码里后面一些是调试用的，在leetcode上提交应去掉

show me the code

class node:
    def __init__(self,val = None):
        self.val = val
        self.isKey = False
        self.children = {}
    def __getitem__(self,i):
        return self.children[i]
    def __iter__(self):
        return iter(self.children.keys())
    def __setitem__(self,i,x):
        self.children[i] = x
    def __bool__(self):
        return self.children!={}
    def __str__(self):
        return 'val: ' str(self.val) '\nchildren: ' ' '.join(self.children.keys())
    def __repr__(self):
        return str(self)

class Trie(object):

    def __init__(self):
        self.root=node('')
        self.dic ={'insert':self.insert,'startsWith':self.startsWith,'search':self.search}

    def insert(self, word):
        """
        Inserts a word into the trie.
        :type word: str
        :rtype: void
        """
        if not word:return 
        nd = self.root
        for i in word:
            if i in nd:
                nd = nd[i]
            else:
                newNode= node(i)
                nd[i] = newNode
                nd = newNode
        else:nd.isKey = True
    def search(self, word):
        """
        Returns if the word is in the trie.
        :type word: str
        :rtype: bool
        """
        nd = self.root
        for i in word:
            if i in nd:
                nd = nd[i]
            else:return False
        else:return nd.isKey
    def startsWith(self, prefix):
        """
        Returns if there is any word in the trie that starts with the given prefix.
        :type prefix: str
        :rtype: bool
        """
        nd = self.root
        for i in prefix:
            if i in  nd:
                nd= nd[i]
            else:return False
        return True
    def display(self):
        print('preOrderTraverse  data of the Trie')
        self.preOrder(self.root,'')
    def preOrder(self,root,s):
        s=s root.val
        if  root.isKey:
            print(s)
        for i in root:
            self.preOrder(root[i],s)

if __name__=='__main__':
    t = Trie()
    rsts = [None,None,None,None,None,None,False,True,False,False,False,False,False,True,True,False,True,True,False,False,False,True,True,True]
    op = ["insert","insert","insert","insert","insert","insert","search","search","search","search","search","search","search","search","search","startsWith","startsWith","startsWith","startsWith","startsWith","startsWith","startsWith","startsWith","startsWith"]
    data = [["app"],["apple"],["beer"],["add"],["jam"],["rental"],["apps"],["app"],["ad"],["applepie"],["rest"],["jan"],["rent"],["beer"],["jam"],["apps"],["app"],["ad"],["applepie"],["rest"],["jan"],["rent"],["beer"],["jam"]]
    for i,datum,rst in zip(op,data,rsts):
        if t.dic[i](datum[0]) != rst:print(i,datum[0],rst)
    t.display()