0208_trie.py

'''
Implement a trie with insert, search, and startsWith methods.

Example:

Trie trie = new Trie();

trie.insert("apple");
trie.search("apple");   // returns true
trie.search("app");     // returns false
trie.startsWith("app"); // returns true
trie.insert("app");   
trie.search("app");     // returns true

来源：力扣（LeetCode）
链接：https://leetcode-cn.com/problems/implement-trie-prefix-tree
著作权归领扣网络所有。商业转载请联系官方授权，非商业转载请注明出处。
'''

class Trie:

    def __init__(self):
        """
        Initialize your data structure here.
        """
        self.trie = {}

    def insert(self, word: str) -> None:
        """
        Inserts a word into the trie.
        """
        curr = self.trie
        for c in word:
            if c not in curr:
                curr[c] = {}
            curr = curr[c]
        curr['#'] = 1
            

    def search(self, word: str) -> bool:
        """
        Returns if the word is in the trie.
        """
        curr = self.trie
        for c in word:
            if c not in curr:
                return False
            curr = curr[c]
        return '#' in curr


    def startsWith(self, prefix: str) -> bool:
        """
        Returns if there is any word in the trie that starts with the given prefix.
        """
        curr = self.trie
        for c in prefix:
            if c not in curr:
                return False
            curr = curr[c]
        return True


# Your Trie object will be instantiated and called as such:
# obj = Trie()
# obj.insert(word)
# param_2 = obj.search(word)
# param_3 = obj.startsWith(prefix)