Python Program To Get Minimum Elements For String Construction

Given a String, the task is to write a Python program to count the minimum elements required to form a string from list elements.

Input : test_list = [“geek”, “ring”, “sfor”, “ok”, “woke”], tar_str = “working” 
Output : 2 
Explanation : working can be formed using woke and ring.

Input : test_list = [“geek”, “ring”, “sfor”, “ok”, “woke”], tar_str = “workinggeek” 
Output : 3 
Explanation : workinggeek can be formed using woke, geek and ring. 

Method : Using issubset() + set() + combinations()

In this, we iterate for a list of strings and form all size combinations, each combination is converted to set and checked to be forming target string using issubset(), if found, the loop is exited and the count is recorded.

Python3

# Python3 code to demonstrate working of
# Minimum elements for String construction
# Using issubset() + set() + combinations()
from itertools import combinations

# initializing list
test_list = ["geek", "ring", "sfor", "ok", "woke"]

# printing original list
print("The original list is : " + str(test_list))

# initializing target string
tar_str = "working"

res = -1
set_str = set(tar_str)
done = False
for val in range(0, len(test_list) + 1):

    # creating combinations
    for sub in combinations(test_list, val):

        # contructing sets of each combinations
        temp_set = set(ele for subl in sub for ele in subl)

        # checking if target string has created set as subset
        if set_str.issubset(temp_set):
            res = val
            done = True
            break
    if done:
        break

# printing result
print("The Minimum count elements for string : " + str(res))

Output:

The original list is : ['geek', 'ring', 'sfor', 'ok', 'woke']
The Minimum count elements for string : 2