# LeetCode: 208. 实现 Trie (前缀树)¶

## 1、题目描述¶

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


• 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。

## 2、解题思路¶

​ 直接用哈希来做，python的话，就用字典实现即可

• 初始化

class Trie:

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

def insert(self, word):
"""
Inserts a word into the trie.
:type word: str
:rtype: void
"""
cur = self.head
for i in word:
if cur.get(i) is None:
cur[i] = {}
cur = cur[i]
if cur.get("end") is None:
cur["end"] = 1

def search(self, word):
"""
Returns if the word is in the trie.
:type word: str
:rtype: bool
"""
cur = self.head
for i in word:
if i not in cur:
return False
cur = cur[i]

if cur.get("end") is not None:
return True
else:
return False

def startsWith(self, prefix):
"""
Returns if there is any word in the trie that starts with the given prefix.
:type prefix: str
:rtype: bool
"""
cur = self.head
for i in prefix:
if i not in cur:
return False
cur = cur[i]

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)