题目链接:https://leetcode-cn.com/problems/implement-trie-prefix-tree/
题目描述:
实现一个 Trie (前缀树),包含 insert
, search
, 和 startsWith
这三个操作。
示例:
Trie trie = new Trie();
trie.insert("apple");
trie.search("apple"); // 返回 true
trie.search("app"); // 返回 false
trie.startsWith("app"); // 返回 true
trie.insert("app");
trie.search("app"); // 返回 true
说明:
- 你可以假设所有的输入都是由小写字母 a-z 构成的。
- 保证所有输入均为非空字符串。
思路:
前缀树,又称字典树
详细可以查看
多种写法,写个简单的!
class Trie:
def __init__(self):
"""
Initialize your data structure here.
"""
self.lookup = {}
def insert(self, word: str) -> None:
"""
Inserts a word into the trie.
"""
tree = self.lookup
for a in word:
if a not in tree:
tree[a] = {}
tree = tree[a]
tree["#"] = "#"
def search(self, word: str) -> bool:
"""
Returns if the word is in the trie.
"""
tree = self.lookup
for a in word:
if a not in tree:
return False
tree = tree[a]
if "#" in tree:
return True
return False
def startsWith(self, prefix: str) -> bool:
"""
Returns if there is any word in the trie that starts with the given prefix.
"""
tree = self.lookup
for a in prefix:
if a not in tree:
return False
tree = tree[a]
return True