[Leetcode] 0208. Implement Trie

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A trie (pronounced as “try”) or prefix tree is a tree data structure used to efficiently store and retrieve keys in a dataset of strings. There are various applications of this data structure, such as autocomplete and spellchecker.

Implement the Trie class:

Trie() Initializes the trie object.
void insert(String word) Inserts the string word into the trie.
boolean search(String word) Returns true if the string word is in the trie (ie, was inserted before), and false otherwise.
boolean startsWith(String prefix) Returns true if there is a previously inserted string word that has the prefix prefix, and false otherwise.

Example 1:

Input
["Trie", "insert", "search", "search", "startsWith", "insert", "search"] [[], ["apple"], ["apple"], ["app"], ["app"], ["app"], ["app"]]
Output
[null, null, true, false, true, null, true]

Explanation
Trie trie = new Trie(); trie.insert("apple"); trie.search("apple"); // return True trie.search("app"); // return False trie.startsWith("app"); // return True trie.insert("app"); trie.search("app"); // return True

Constraints:

1 <= word.length, prefix.length <= 2000
word and prefix consist only of lowercase English letters.
At most 3 * 10 ⁴ calls in total will be made to insert, search, and startsWith.

内容目录

Python

				
					# insert() # time complexity: O(l) # space complexity: O(l) # search() # time complexity: O(l) # space complexity: O(1) # search prefix() # time complexity: O(l) # space complexity: O(1) class TrieNode: def __init__(self, char: str = ""): self.char = char self.children = {} self.isEnd = False class Trie: def __init__(self): self.root = TrieNode() def insert(self, word: str): node = self.root for c in word: if c in node.children: node = node.children[c] else: newNode = TrieNode() node.children[c] = newNode node = newNode node.isEnd = True def search(self, word: str): node = self.root for c in word: if c not in node.children: return False node = node.children[c] return node.isEnd def startsWith(self, prefix: str): node = self.root for c in prefix: if c not in node.children: return False node = node.children[c] return True # Your Trie object will be instantiated and called as such: trie = Trie() trie.insert("apple") print(trie.search("apple")) print(trie.search("app")) print(trie.startsWith("app")) trie.insert("app") print(trie.search("app"))

Python

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