Add and Search Word - Data structure design
要点:类似的题做过n多遍了,不容易记的地方就是call递归函数之前要创建结点表示当前的字符。当递归过界的时候,表示没有当前字符,所以直接返回而不创建+进一步递归
错误点:注意None and如果hit None的branch整个式子返回None而不是False,当然如果作为if的条件是无所谓的,因为None自动转为False。但是作为返回结果就不对了。
class WordDictionary(object):
class TrieNode:
def __init__(self):
self.neighbors = [None]*26
self.isLeaf = False
def __init__(self):
"""
initialize your data structure here.
"""
self.root = self.TrieNode()
def addWord(self, word):
"""
Adds a word into the data structure.
:type word: str
:rtype: void
"""
def addRec(root, start, word):
n = len(word)
if start==n:
root.isLeaf = True
return
c = ord(word[start])-ord('a')
if not root.neighbors[c]:
root.neighbors[c] = self.TrieNode()
addRec(root.neighbors[c], start+1, word)
addRec(self.root, 0, word)
def search(self, word):
"""
Returns if the word is in the data structure. A word could
contain the dot character '.' to represent any one letter.
:type word: str
:rtype: bool
"""
def searchRec(root, start, word):
n = len(word)
if start==n:
if root.isLeaf:
return True
else:
return False
if word[start]=='.':
for t in root.neighbors:
if t and searchRec(t, start+1, word):
return True
return False
else:
c = ord(word[start])-ord('a')
return root.neighbors[c] is not None and searchRec(root.neighbors[c], start+1, word)
return searchRec(self.root, 0, word)
# Your WordDictionary object will be instantiated and called as such:
# wordDictionary = WordDictionary()
# wordDictionary.addWord("word")
# wordDictionary.search("pattern")