LeetCode 127 Word Ladder

import string
class Solution(object):
    def ladderLength(self, beginWord, endWord, wordList):
        """
        :type beginWord: str
        :type endWord: str
        :type wordList: Set[str]
        :rtype: int
        """
        # two way bfs
        # one way is not sufficient
        wordList.discard(beginWord)
        wordList.discard(endWord)
        hash_map, res = {}, []
        res = self.bfs(set([beginWord]), set([endWord]), wordList, 2)
        return res

    def bfs(self, forward, backward, wordlist, level):
        if len(forward) == 0 or len(backward) == 0:
            return 0
        if len(forward) > len(backward):
            return self.bfs(backward, forward, wordlist, level)
        is_connected = False
        next_level = set()
        for word in forward:
            for c in string.ascii_lowercase:
                for index in range(len(word)):
                    neigh = word[:index] + c + word[index + 1:]
                    if neigh in backward:
                        is_connected = True
                        return level
                    if not is_connected and neigh in wordlist:
                        next_level.add(neigh)
                        wordlist.discard(neigh)
        if not is_connected:
            return self.bfs(next_level, backward, wordlist, level + 1)


if __name__ == "__main__":
    s = Solution()
    # print s.ladderLength('hit', 'cog', set(["hot","dot","dog","lot","log"]))
    # print s.ladderLength('a', 'b', set(['a', 'b', 'c']))
    # print s.ladderLength('hot', 'dog', set(['hot', 'dog']))
    # print s.ladderLength("qa", "sq", set(["si","go","se","cm","so","ph","mt","db","mb","sb","kr","ln","tm","le","av","sm","ar","ci","ca","br","ti","ba","to","ra","fa","yo","ow","sn","ya","cr","po","fe","ho","ma","re","or","rn","au","ur","rh","sr","tc","lt","lo","as","fr","nb","yb","if","pb","ge","th","pm","rb","sh","co","ga","li","ha","hz","no","bi","di","hi","qa","pi","os","uh","wm","an","me","mo","na","la","st","er","sc","ne","mn","mi","am","ex","pt","io","be","fm","ta","tb","ni","mr","pa","he","lr","sq","ye"]))
    # print s.ladderLength("hot", "dog", set(["hot","cog","dog","tot","hog","hop","pot","dot"]))
    # print s.ladderLength("sand", "acne", set(["slit","bunk","wars","ping","viva","wynn","wows","irks","gang","pool","mock","fort","heel","send","ship","cols","alec","foal","nabs","gaze","giza","mays","dogs","karo","cums","jedi","webb","lend","mire","jose","catt","grow","toss","magi","leis","bead","kara","hoof","than","ires","baas","vein","kari","riga","oars","gags","thug","yawn","wive","view","germ","flab","july","tuck","rory","bean","feed","rhee","jeez","gobs","lath","desk","yoko","cute","zeus","thus","dims","link","dirt","mara","disc","limy","lewd","maud","duly","elsa","hart","rays","rues","camp","lack","okra","tome","math","plug","monk","orly","friz","hogs","yoda","poop","tick","plod","cloy","pees","imps","lead","pope","mall","frey","been","plea","poll","male","teak","soho","glob","bell","mary","hail","scan","yips","like","mull","kory","odor","byte","kaye","word","honk","asks","slid","hopi","toke","gore","flew","tins","mown","oise","hall","vega","sing","fool","boat","bobs","lain","soft","hard","rots","sees","apex","chan","told","woos","unit","scow","gilt","beef","jars","tyre","imus","neon","soap","dabs","rein","ovid","hose","husk","loll","asia","cope","tail","hazy","clad","lash","sags","moll","eddy","fuel","lift","flog","land","sigh","saks","sail","hook","visa","tier","maws","roeg","gila","eyes","noah","hypo","tore","eggs","rove","chap","room","wait","lurk","race","host","dada","lola","gabs","sobs","joel","keck","axed","mead","gust","laid","ends","oort","nose","peer","kept","abet","iran","mick","dead","hags","tens","gown","sick","odis","miro","bill","fawn","sumo","kilt","huge","ores","oran","flag","tost","seth","sift","poet","reds","pips","cape","togo","wale","limn","toll","ploy","inns","snag","hoes","jerk","flux","fido","zane","arab","gamy","raze","lank","hurt","rail","hind","hoot","dogy","away","pest","hoed","pose","lose","pole","alva","dino","kind","clan","dips","soup","veto","edna","damp","gush","amen","wits","pubs","fuzz","cash","pine","trod","gunk","nude","lost","rite","cory","walt","mica","cart","avow","wind","book","leon","life","bang","draw","leek","skis","dram","ripe","mine","urea","tiff","over","gale","weir","defy","norm","tull","whiz","gill","ward","crag","when","mill","firs","sans","flue","reid","ekes","jain","mutt","hems","laps","piss","pall","rowe","prey","cull","knew","size","wets","hurl","wont","suva","girt","prys","prow","warn","naps","gong","thru","livy","boar","sade","amok","vice","slat","emir","jade","karl","loyd","cerf","bess","loss","rums","lats","bode","subs","muss","maim","kits","thin","york","punt","gays","alpo","aids","drag","eras","mats","pyre","clot","step","oath","lout","wary","carp","hums","tang","pout","whip","fled","omar","such","kano","jake","stan","loop","fuss","mini","byrd","exit","fizz","lire","emil","prop","noes","awed","gift","soli","sale","gage","orin","slur","limp","saar","arks","mast","gnat","port","into","geed","pave","awls","cent","cunt","full","dint","hank","mate","coin","tars","scud","veer","coax","bops","uris","loom","shod","crib","lids","drys","fish","edit","dick","erna","else","hahs","alga","moho","wire","fora","tums","ruth","bets","duns","mold","mush","swop","ruby","bolt","nave","kite","ahem","brad","tern","nips","whew","bait","ooze","gino","yuck","drum","shoe","lobe","dusk","cult","paws","anew","dado","nook","half","lams","rich","cato","java","kemp","vain","fees","sham","auks","gish","fire","elam","salt","sour","loth","whit","yogi","shes","scam","yous","lucy","inez","geld","whig","thee","kelp","loaf","harm","tomb","ever","airs","page","laud","stun","paid","goop","cobs","judy","grab","doha","crew","item","fogs","tong","blip","vest","bran","wend","bawl","feel","jets","mixt","tell","dire","devi","milo","deng","yews","weak","mark","doug","fare","rigs","poke","hies","sian","suez","quip","kens","lass","zips","elva","brat","cosy","teri","hull","spun","russ","pupa","weed","pulp","main","grim","hone","cord","barf","olav","gaps","rote","wilt","lars","roll","balm","jana","give","eire","faun","suck","kegs","nita","weer","tush","spry","loge","nays","heir","dope","roar","peep","nags","ates","bane","seas","sign","fred","they","lien","kiev","fops","said","lawn","lind","miff","mass","trig","sins","furl","ruin","sent","cray","maya","clog","puns","silk","axis","grog","jots","dyer","mope","rand","vend","keen","chou","dose","rain","eats","sped","maui","evan","time","todd","skit","lief","sops","outs","moot","faze","biro","gook","fill","oval","skew","veil","born","slob","hyde","twin","eloy","beat","ergs","sure","kobe","eggo","hens","jive","flax","mons","dunk","yest","begs","dial","lodz","burp","pile","much","dock","rene","sago","racy","have","yalu","glow","move","peps","hods","kins","salk","hand","cons","dare","myra","sega","type","mari","pelt","hula","gulf","jugs","flay","fest","spat","toms","zeno","taps","deny","swag","afro","baud","jabs","smut","egos","lara","toes","song","fray","luis","brut","olen","mere","ruff","slum","glad","buds","silt","rued","gelt","hive","teem","ides","sink","ands","wisp","omen","lyre","yuk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