原题：

211. Add and Search Word - Data structure design

Design a data structure that supports the following two operations:

void addWord(word)
bool search(word)

search(word) can search a literal word or a regular expression string containing only letters a-z or .. A . means it can represent any one letter.

Example:

addWord("bad")
addWord("dad")
addWord("mad")
search("pad") -> false
search("bad") -> true
search(".ad") -> true
search("b..") -> true

Note:
You may assume that all words are consist of lowercase letters a-z.

总结：栈 stack 的利用，先进后出的作用，可以保持 链表一类的数据的连贯操作，可以用来替代广度搜索。

每一层次可以用进栈出栈进行替代。
stack=[（node,str）],形式的数据结构，有记忆状态的作用。
应用： 字符串的遍历，广度搜索。
    

import collections

class WordNode:
    def __init__(self):
        self.children = {}
        self.isEnd = False

class WordDictionary:
    def __init__(self):
        self.root = WordNode()

    def addWord(self, word):
        cur_node=self.root
        for char_iter in word:
            if char_iter in cur_node.children:
                cur_node=cur_node.children[char_iter]
            else:
                new_node=WordNode()
                cur_node.children[char_iter]=new_node
                cur_node=new_node
            # cur_node=cur_node.children[char_iter]
        cur_node.isEnd=True

    def search(self, word):
        stack=[(self.root,word)]
        while stack:
            node,w=stack.pop()
            if not w:
                if node.isEnd:
                    return True
            # print([w])
            elif w[0] == '.':
                for node_iter in node.children.values():
                    stack.append((node_iter,w[1:]))
            elif w[0] in node.children:
                nodes_cur=node.children[w[0]]
                stack.append((nodes_cur,w[1:]))
            else:
                pass
        return False




class WordDictionary:
    def __init__(self):
        self.root = WordNode()

    def addWord(self, word):
        node = self.root
        for w in word:
            if w in node.children:
                node = node.children[w]
            else:
                node.children[w] = WordNode()
                node = node.children[w]
        node.isEnd = True

    def search(self, word):
        stack = [(self.root, word)]
        while stack:
            node, w = stack.pop()
            if not w:
                if node.isEnd:
                    return True
            elif w[0] == '.':
                for n in node.children.values():
                    stack.append((n, w[1:]))
            else:
                if w[0] in node.children:
                    n = node.children[w[0]]
                    stack.append((n, w[1:]))
        return False


if __name__=='__main__':
    wd=WordDictionary()
    # wd.addWord("bad")
    # wd.addWord("dad")
    # wd.addWord("mad")
    # out=wd.search("pad")
    # print(out)
    # out =wd.search("bad")
    # print(out)
    # out =wd.search(".ad")
    # print(out)
    # out =wd.search("b..")
    # print(out)

    words=["WordDictionary", "addWord", "addWord", "search", "search", "search", "search", "search", "search"]
    detect_words=[ ["a"], ["a"], ["."], ["a"], ["aa"], ["a"], [".a"], ["a."]]
    for word in words:
        wd.addWord(word)
    for detect_word in detect_words:
        out=wd.search(detect_word[0])
        print(out)