Basic Cryptanalysis.py

# Author : Tonmoy M
# GitHub URL : https://qinetique.github.io
# Problem : Basic Cryptanalysis
# Problem Sub-Domain : Security | Cryptography
# Problem Domain : HackerRank
# Problem URL : https://www.hackerrank.com/challenges/basic-cryptanalysis/problem?isFullScreen=true

import re

f = open('dictionary.lst', 'r')
data = f.read().lower()
f.close()
words = data.split()
wordmap = {}
for word in words:
    length = len(word)
    sub = wordmap.get(length, {})
    wordmap[length] = sub
    gen = ''
    for c in word:
        if c not in gen:
            gen += c
    key = [0] * length
    for i, c in enumerate(word):
        key[i] = gen.index(c)
    key = ' '.join([str(k) for k in key])
    arr = sub.get(key, [])
    sub[key] = arr
    arr.append(word)

alpha = 'abcdefghijklmnopqrstuvwxyz'
cypher = ['.'] * 26
data = input()
enc = data.split()
fn = enc[:]


def i_dnt_know():
    global fn, cypher, alpha, wordmap
    for word in fn:
        length = len(word)
        gen = ''
        for c in word:
            if c not in gen:
                gen += c
        key = [0] * length
        pattern = ''
        for i, c in enumerate(word):
            key[i] = gen.index(c)
            try:
                j = cypher.index(c)
                pattern += alpha[j]
            except:
                pattern += '.'
        key = ' '.join([str(k) for k in key])
        matches = wordmap[length][key]
        copy = []
        for match in matches:
            if re.fullmatch(pattern, match):
                copy.append(match)
        matches = copy
        if len(matches) == 1:
            fn.remove(word)
            match = matches[0]
            for i in range(length):
                x = alpha.index(match[i])
                cypher[x] = word[i]


i = len(fn)
while True:
    i_dnt_know()
    j = len(fn)
    if i == j:
        break
    i = j
cypher = ''.join(cypher)
output = [' '] * len(data)
for i, c in enumerate(data):
    if c is not ' ':
        output[i] = alpha[cypher.index(c)]
print(''.join(output))