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Python – Retain smallest subsets from strings

  • Last Updated : 21 Apr, 2021

Given a set of strings, the task is to write a python program to retain strings from sets that are the smallest possible subset of strings found. 

Input : test_set = {‘cbabca’, ‘cba’, ‘bdb’, ‘bdbab’, ‘abcx’}

Output : {‘bdb’, ‘abcx’, ‘cba’}

Explanation : bdbab is removed as bdb ( smaller subset ) is retained.

Input : test_set = {‘cbabca’, ‘cba’,  ‘bdbab’, ‘abcx’}

Output : {‘bdbab’, ‘abcx’, ‘cba’}

Explanation : cbabca is removed as cba ( smaller subset ) is retained.

Method : Using sorted() + any() + string slicing 

In this, we perform the task of getting the smallest of substrings by sorting the substring set and use any() to test if any of the subset matches the substring of string present in strings extracted as results smaller than the current string, and also a subset of a string. 


# Python3 code to demonstrate working of
# Retain smallest subsets from string
# Using sorted() + any() + string slicing
# initializing strings set
test_set = {'cbabca', 'cba', 'bdb', 'bdbab', 'abcx'}
# printing original string
print("The original set is : " + str(test_set))
res = set()
for st_r in sorted(test_set, key=len):
    # getting smallest set and checking for already 
    # present smaller set for subset
    if not any(st_r[idx: idx + y + 1] in res 
               for idx in range(len(st_r)) 
               for y in range(len(st_r) - idx)):
# printing result
print("Required extracted strings : " + str(res))


The original set is : {'cba', 'abcx', 'bdb', 'bdbab', 'cbabca'}
Required extracted strings : {'abcx', 'cba', 'bdb'}

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