题目
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。
解答
class Trie:
def __init__(self):
"""
Initialize your data structure here.
"""
self.root = TreeNode()
def insert(self, word: str) -> None:
"""
Inserts a word into the trie.
"""
# 从根节点出发
node = self.root
for char in word:
if char not in node.children: # 判断当前字符是否在当前节点的子节点里面,不在,则创建一个子节点
node.children[char] = TreeNode()
node = node.children[char] # 跳到对应的子节点
node.word = True
def search(self, word: str) -> bool:
"""
Returns if the word is in the trie.
"""
node = self.root
for char in word:
if char not in node.children:
return False
node = node.children[char]
return node.word
def startsWith(self, prefix: str) -> bool:
"""
Returns if there is any word in the trie that starts with the given prefix.
"""
node = self.root
for char in prefix:
if char not in node.children:
return False
node = node.children[char]
return True
测试验证
class TreeNode:
def __init__(self):
self.word = False # 表示当前节点是否是一个曾经插入的单词
self.children = {} # 子节点列表
class Trie:
def __init__(self):
"""
Initialize your data structure here.
"""
self.root = TreeNode()
def insert(self, word: str) -> None:
"""
Inserts a word into the trie.
"""
# 从根节点出发
node = self.root
for char in word:
if char not in node.children: # 判断当前字符是否在当前节点的子节点里面,不在,则创建一个子节点
node.children[char] = TreeNode()
node = node.children[char] # 跳到对应的子节点
node.word = True
def search(self, word: str) -> bool:
"""
Returns if the word is in the trie.
"""
node = self.root
for char in word:
if char not in node.children:
return False
node = node.children[char]
return node.word
def startsWith(self, prefix: str) -> bool:
"""
Returns if there is any word in the trie that starts with the given prefix.
"""
node = self.root
for char in prefix:
if char not in node.children:
return False
node = node.children[char]
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)
if __name__ == '__main__':
obj = Trie()
obj.insert("apple")
print(obj.search("apple"), "= True")
print(obj.search("app"), "= False")
print(obj.startsWith("app"), "= True")
obj.insert("app")
print(obj.search("app"), "= True")
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