tire 树 也叫字典树，也是一种 N 叉树，是一种特殊的前缀树结构。
1、前缀树是N叉树的一种特殊形式。通常来说，一个前缀树是用来存储字符串的。前缀树的每一个节点代表一个字符串（前缀）。每一个节点会有多个子节点，通往不同子节点的路径上有着不同的字符。子节点代表的字符串是由节点本身的原始字符串，以及通往该子节点路径上所有的字符组成的。
下面是前缀树的一个例子：
前缀树的一个重要的特性是，节点所有的后代都与该节点相关的字符串有着共同的前缀。这就是前缀树名称的由来。
2、实现tire 树的插入和搜索、以及根据前缀判断是否在trie树操作方式：
下面用几种方式来实现
class Trie:
def __init__(self):
"""
Initialize your data structure here.
"""
self.root = {}
self.end = -1
def insert(self, word):
"""
Inserts a word into the trie.
:type word: str
:rtype: void
"""
curNode = self.root
for c in word:
if not c in curNode:
curNode[c] = {}
curNode = curNode[c]
curNode[self.end] = True
def search(self, word):
"""
Returns if the word is in the trie.
:type word: str
:rtype: bool
"""
curNode = self.root
for c in word:
if not c in curNode:
return False
curNode = curNode[c]
# Doesn't end here
if not self.end in curNode:
return False
return True
def startsWith(self, prefix):
"""
Returns if there is any word in the trie that starts with the given prefix.
:type prefix: str
:rtype: bool
"""
curNode = self.root
for c in prefix:
if not c in curNode:
return False
curNode = curNode[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)第二种查看别人提交的代码，觉得比较好理解。
class Trie:
# word_end = -1
def __init__(self):
"""
Initialize your data structure here.
"""
self.root = {}
self.word_end = -1
def insert(self, word):
"""
Inserts a word into the trie.
:type word: str
:rtype: void
"""
curNode = self.root
for c in word:
if not c in curNode:
curNode[c] = {}
curNode = curNode[c]
curNode[self.word_end] = True
def search(self, word):
"""
Returns if the word is in the trie.
:type word: str
:rtype: bool
"""
curNode = self.root
for c in word:
if not c in curNode:
return False
curNode = curNode[c]
# Doesn't end here
if self.word_end not in curNode:
return False
return True
def startsWith(self, prefix):
"""
Returns if there is any word in the trie that starts with the given prefix.
:type prefix: str
:rtype: bool
"""
curNode = self.root
for c in prefix:
if not c in curNode:
return False
curNode = curNode[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)第三种方式也是在博客看别人的代码，觉得写的也很好。
class Trie:
def __init__(self):
"""
Initialize your data structure here.
"""
self.root = TrieNode()
def insert(self, word):
"""
Inserts a word into the trie.
:type word: str
:rtype: void
"""
node = self.root
for chars in word:
child = node.data.get(chars)
if not child :
node.data[chars] = TrieNode()
node = node.data[chars]
node.is_word = True
def search(self, word):
"""
Returns if the word is in the trie.
:type word: str
:rtype: bool
"""
node = self.root
for chars in word:
node = node.data.get(chars)
if not node:
return False
return node.is_word # 判断单词是否是完整的存在在trie树中
def startsWith(self, prefix):
"""
Returns if there is any word in the trie that starts with the given prefix.
:type prefix: str
:rtype: bool
"""
node = self.root
for chars in prefix:
node = node.data.get(chars)
if not node:
return False
return True
def get_start(self, prefix):
"""
Returns words started with prefix
:param prefix:
:return: words (list)
"""
def get_key(pre, pre_node):
word_list = []
if pre_node.is_word:
word_list.append(pre)
for x in pre_node.data.keys():
word_list.extend(get_key(pre + str(x), pre_node.data.get(x)))
return word_list
words = []
if not self.startsWith(prefix):
return words
if self.search(prefix):
words.append(prefix)
return words
node = self.root
for chars in prefix:
node = node.data.get(chars)
return get_key(prefix, node)
trie = Trie()
trie.insert("something")
trie.insert("somebody")
trie.insert("somebody1")
trie.insert("somebody3")
print(trie.search("key"))
print(trie.search("somebody3"))
print(trie.get_start('some'))上述写的几种方法都有参考别人的写法，其他博主请见谅。
