Python | Words extraction from set of characters using dictionary

Given the words, the task is to extract different words from a set of characters using the defined dictionary. Approach: Python in its language defines an inbuilt module enchant which handles certain operations related to words. In the approach mentioned, following methods are used.

• check() : It checks if a string is a word or not and returns true if a string is a word, else returns false.
• permutations(str_arr, str_len) : It provides the combination of a string as per the mentioned string length.

There is a chance that enchant() module might not be present, so it can be installed using pip3 install enchant. Below is the Python code implementation of the above approach.

Python3

# importing libraries
import keyword
import enchant
from itertools import permutations

d = enchant.Dict("en_US")

words = []
perm_word = []

# character combination to
# list down all the words
str_arr = "star"

# Getting the string length to use it in the loop.
str_len = 4
print("Length of the string is : ", str_len )

while str_len > 1 :

    if str_len == len(str_arr):
        perm = list(permutations(str_arr))
        str_len = str_len -1

        for i in list(perm):
            words =''.join(i)

            if d.check(words):
                perm_word.append(words)
                print ( words + " is an English words")
        print ("perm_word", perm_word)

    elif str_len > 1:
        perm = list(permutations(str_arr, str_len))
        str_len = str_len -1

        for i in list(perm):
            words =''.join(i)

            if d.check(words):
                perm_word.append(words)
                print ( words + " is an English word")
        print ("perm_word", perm_word)

    else:
        str_len = 0

Output : 

star is an English words
tars is an English words
arts is an English words
rats is an English words
perm_word [‘star’, ‘tars’, ‘arts’, ‘rats’]
sat is an English word
tar is an English word
art is an English word
rat is an English word
perm_word [‘star’, ‘tars’, ‘arts’, ‘rats’, ‘sat’, ‘tar’, ‘art’, ‘rat’]
st is an English word
ts is an English word
tr is an English word
as is an English word
at is an English word
rs is an English word
rt is an English word
perm_word [‘star’, ‘tars’, ‘arts’, ‘rats’, ‘sat’, ‘tar’, ‘art’, ‘rat’, 
‘st’, ‘ts’, ‘tr’, ‘as’, ‘at’, ‘rs’, ‘rt’]

Time complexity : O(n!) It generates all possible permutations of the given string and then checks if the permuted word is present in the English dictionary. The total number of permutations is n! (n factorial), where n is the length of the string, so the time complexity is O(n!).

Space complexity : O(n!) This is because the permutations are stored in a list called “perm_word”. For each iteration of the while loop, the list grows with the number of possible permutations, which is given by n!. So the space complexity is proportional to the number of permutations stored in the list, which is O(n!).