how this tricky problem could be solved in python for creating subarray

Question

write a program to create subset of given array the value inside the array should be target value and length of array should be k

program that i have tried

arr = [1, 2, 8, 6, 4, 9, 5]
k = 3
target = 10
sub = []
res = []

for i in arr:
    sub.append(i)
    if len(sub) == k:
        if sum(sub) == target:
            res.append(sub[:])  
        sub.pop(0) 
print(res)

sample input: arr = [1,2,3,6,4,9,5] k = 3 target = 10 output =: [1,4,5]

This is called the subset sum problem. See towardsdatascience.com/… — Abhijit Sarkar
– Abhijit Sarkar, Commented Nov 2, 2023 at 11:14
@AbhijitSarkar, suggest a free page rather than a page that says: The author made this story available to Medium members only. Upgrade to instantly unlock this story plus other member-only benefits. — Bibhav
– Bibhav, Commented Nov 2, 2023 at 11:16
@AbhijitSarkar So, don't suggest a link if it does not help. As simple as that. — Bibhav
– Bibhav, Commented Nov 2, 2023 at 11:23
Unironically why was OP downvoted? They actually have their attempt as well in the question. smh 🤦‍♀️. Insert r/programmerhumor StackOverflow helpfulness meme here. — Sash Sinha
– Sash Sinha, Commented Nov 2, 2023 at 11:31
@SashSinha Very likely because the question is pretty common and OP has not demonstrated any research effort. They also didn’t say what their problem is. — Abhijit Sarkar
– Abhijit Sarkar, Commented Nov 2, 2023 at 11:42

Bibhav · Accepted Answer · 2023-11-03 16:35:59Z

-1

Use of itertools.combinations would be best here:

from itertools import combinations

arr = [1, 2, 8, 6, 4, 9, 5]
k = 3
target = 10

subsets = [comb for comb in combinations(arr, k) if sum(comb) == target]
print(subsets)

This results in list of tuple not list to consider the chances of having other such combinations, despite the example showcasing only one.

If you want a custom combinations function you can create one by use of recursion:

def combinations(arr, k):
    if k == 0:
        return [[]]
    if not arr:
        return []
    head, *tail = arr
    return [[head] + combo for combo in combinations(tail, k - 1)] + combinations(tail, k)

edited Nov 3, 2023 at 16:35

answered Nov 2, 2023 at 11:05

Bibhav

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2 Comments

Abhijit Sarkar Over a year ago

This is extremely inefficient to the point of being impractical for large n. If there are n integers in the list, there exist 2^n — 1 subsets that need to be checked (excluding the empty set).

6004 Abdul Rahman Harris Over a year ago

so how can we approach this problem without use of itertools.combination

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