如何使用马尔可夫链获得所有可能性？

Question

I am trying to implement a linguistic passphrase cracker using markov chains.

The idea behind this is to chose n-grams from a text, select a starting n-gram (usually a word that is at the beginning of a sentence) and represent it as a state, using the first n-1 characters. As an example, for "the" I will have "th". This will have a list of letters with their occurences, and will be represented as a dictionary. dict["th"] = [('e', 120), ('a', 79)] etc. For each of these values I will try to create a markov chain that will satisfy either my password or my password length. What that means is that when the markov chain has the same length as my password that I am trying to find, I will stop the execution and check if the markov chain is the same with my password. I am trying to implement this using a recursive function but for some reason I am getting stack overflow.

def ceva(myTry, good_all, pwd, guess, level):
        save = myTry
        if len(pwd) == len(guess):
            if pwd == guess:
                return 1
        else:
            if myTry in good_all.keys():
                values = good_all[myTry]
                for i in range(0,len(values)):
                    #print(i, len(values))
                    letter = values[i][0]
                    #print("First",myTry, letter)

                    pwd += letter
                    if i != len(values)-1:

                        if len(pwd) == len(guess):
                            #print("In if", pwd, myTry)
                            if pwd == guess:
                                print("I found:", pwd)
                                return 1
                            else:

                                pwd = pwd[0:len(pwd)-1]
                        else:

                            myTry += letter
                            myTry = myTry[1:]
                            #print("In else: ",pwd, myTry)
                            return ceva(myTry, good_all, pwd, guess, level)
                    else:
                        if len(pwd) == len(guess):
                            #print("In if", pwd, myTry)
                            if pwd == guess:
                                print("I found:", pwd)
                                return 1

                        pwd = pwd[0:len(pwd)-1]


    for key, letterList in starter_follows.items():
        myTry = key.replace("_", "")

        # i will not treat the case when the starting phrase
        # is a single character
        if myTry == "i":
            pass
        else:
            for letter in letterList:

                if letter[0] not in "_.-\"!":
                    myTry += letter[0]
                    pwd = copy.copy(myTry)
                    #print("Starter:", pwd)
                    res=ceva(myTry, good_all, pwd, toGuess, 1)
                    myTry = myTry[0:len(myTry)-1]

With this algorithm i am reaching the maximum recursion depth. But I am trying to obtain all the markov chains until the passphrase is found.

EDIT 1: Now, with the updated code, the password is found but only because I am looping thorugh all the possible last letters.

Eg: "indeed"

ind is already in my list of starters, and all the tri-grams I am finding have "e" as their most common next letter. So e is added, then the next e, then a next e and now the password is "indeee", but i am slicing the last letter and going through the for again, and it ultimately finds "indeed", which is okay. The problem is that if I will give indedd it will not find my password, because the second "d" is never looped through. How can I go back in my iteration and loop through all possible letters at all levels?

Answer 1

I managed to pull it off eventually thanks to the answers given. I am posting the working algorithm in hope that it will help someone someday.

def ceva(myTry, good_all, pwd, guess, flag):

if len(pwd) > len(guess):
    return 0
if len(pwd) == len(guess):
    if pwd == guess:
        flag = 1
        return 1
    else: 
        return 0
save = copy.copy(myTry)
#print("Start of functionn:", "[", pwd, ",", myTry, "]")

if flag == 1:
    return 1
else:   

    if myTry in good_all.keys():
        # get the list of letters for this specific trigram
        values = good_all[myTry]

        if len(pwd) <= len(guess):
            for i in range(0,len(values)):
                #myTry = copy.copy(save)
                # get the letter
                letter = values[i][0]

                # add the letter to the password
                pwd += letter


                # if i found the password, set flag to 1 and break the loop
                if pwd == guess:
                    flag = 1
                    print("I found:", pwd)
                    return 1

                # add the new letter to the trigram, and the get rid of the first
                # letter, in order to create the new trigram
                myTry += letter
                myTry = myTry[1:]
                #print("Pwd before cutting: [", pwd, "]")
                res = ceva(myTry, good_all, pwd, guess, flag)
                #print(res)
                if res == 0:
                    pwd = pwd[0:len(pwd)-1]
                    myTry = pwd[-3:]
                #   print("This is after stop: [", pwd,",", myTry, "]")
                else:
                    return 1


    if flag == 0:
        return 0
    else:
        return 1

flag = 0

for key, letterList in starter_follows.items():
    myTry = key.replace("_", "")
    # i will not treat the case when the starting phrase
    # is a single character
    if myTry == "i":
        pass

    else:
        #print("Aaaa")
        for letter in letterList:

            if letter[0] not in "_.-\"!":

                # add the letter to create a (n-1)-gram
                myTry += letter[0]
                # create a copy of the starting password
                pwd = copy.copy(myTry)

                # call the recursive function
                res=ceva(myTry, good_all, pwd, toGuess, flag)
                # go back to the begining, to try a new start
                # e.g.: "the" first, "tha" second
                myTry = myTry[0:len(myTry)-1]