Python – K length Combinations from given characters
Given a string, generate K-length combinations in a one-liner.
Input : test_str = ‘gfg’, K = 3
Output : [‘ggg’, ‘ggf’, ‘ggg’, ‘gfg’, ‘gff’, ‘gfg’, ‘ggg’, ‘ggf’, ‘ggg’, ‘fgg’, ‘fgf’, ‘fgg’, ‘ffg’, ‘fff’, ‘ffg’, ‘fgg’, ‘fgf’, ‘fgg’, ‘ggg’, ‘ggf’, ‘ggg’, ‘gfg’, ‘gff’, ‘gfg’, ‘ggg’, ‘ggf’, ‘ggg’]
Explanation : All combinations of K length extracted.Input : test_str = ‘G4G’, K = 2
Output : [‘GG’, ‘G4’, ‘GG’, ‘4G’, ’44’, ‘4G’, ‘GG’, ‘G4’, ‘GG’]
Explanation : All combinations of K length extracted.
Method #1 : Using itertools.product() + join() + map()
The task can be performed by product() using repeat param, but returns the result in a tuples list of individual characters. These all can be joined using join() and map().
Python3
# Python3 code to demonstrate working of # K length Combinations from given characters shorthand# Using itertools.product() + join() + map()from itertools import product# initializing stringtest_str = 'gf4g'# printing original stringprint("The original string is : " + str(test_str))# initializing K K = 2# map and join() used to change return data typeres = list(map(''.join, product(test_str, repeat = K))) # printing result print("The generated Combinations : " + str(res)) |
The original string is : gf4g The generated Combinations : ['gg', 'gf', 'g4', 'gg', 'fg', 'ff', 'f4', 'fg', '4g', '4f', '44', '4g', 'gg', 'gf', 'g4', 'gg']
Time Complexity: O(n)
Auxiliary Space: O(1)
Method #2 : Using itertools.product() + list comprehension
In this, list comprehension is used for the task of joining elements.
Python3
# Python3 code to demonstrate working of # K length Combinations from given characters shorthand# Using itertools.product() + join() + map()from itertools import product# initializing stringtest_str = 'gfg'# printing original stringprint("The original string is : " + str(test_str))# initializing K K = 2# list comprehension + join() used to change return data typeres = [''.join(ele) for ele in product(test_str, repeat = K)] # printing result print("The generated Combinations : " + str(res)) |
The original string is : gfg The generated Combinations : ['gg', 'gf', 'gg', 'fg', 'ff', 'fg', 'gg', 'gf', 'gg']
Time Complexity: O(n)
Auxiliary Space: O(1)
