CODEWITHSUNDEEP
arrayscombinatorics
jekelija
jekelija

Reputation: 277

How to create all possible enumerations of multiple arrays

I think this is somewhat a combinatorics problem, but its been so long since i've done that that im quite rusty. I have a dynamic number of arrays, each with a dynamic number of elements. I am trying to get the unique combination of all items within each array. For example, if I have 3 arrays

['a','b','c']
['d',e']
['f','g']

Then i would expect to get

['a','d','f'],
['a','e','f'],
['a','d','g'],
['a','e','g'],
['b','d','f'],
['b','e','f'],
['b','d','g'],
['b','e','g'],
['c','d','f'],
['c','e','f'],
['c','d','g'],
['c','e','g']

Really struggling to write the code dynamically since the number of arrays and the number of elements in each array is not known ahead of time.

Upvotes: 0

Views: 45

Answers (2)

Foolhardy Hardy
Foolhardy Hardy

Reputation: 146

I think your problem can solved using a recursive algorithm:

Input: arrs (a array of arrays)

Output: combs (array of all possible combinations)

arrs = ??? # this variable provide input arrays, like [[1,2,3], [4,5]]
combs = [] # this variable store the answer 
def get_combs(arrs, i, currentComb):
    if i >= len(arrs):
        combs.append(list(currentComb))
        return
    for elem in arrs[i]:
        currentComb.append(elem)
        get_combs(arrs, i+1, currentComb)
        currentComb.pop()

get_combs(arrs, 0, []) // after this call, the combs get the desired answer.

The code above is in Python and pretty dirty.

Upvotes: 1

Gowtham Jayachandiran
Gowtham Jayachandiran

Reputation: 118

Using Python, we can achieve this in multiple ways,

a = ['a','b','c']
b = ['d','e']
c = ['f','g']

  1. Using Multiple FOR Loops

     for i in a:
     for j in b:
         for k in c:
             print([i, j, k])

Output:

['a', 'd', 'f']
['a', 'd', 'g']
['a', 'e', 'f']
['a', 'e', 'g']
['b', 'd', 'f']
['b', 'd', 'g']
['b', 'e', 'f']
['b', 'e', 'g']
['c', 'd', 'f']
['c', 'd', 'g']
['c', 'e', 'f']
['c', 'e', 'g']

  1. Using Lists Comprehensions:

     d = [[i, j, k] for i in a for j in b for k in c]
 d

** Output:**

[['a', 'd', 'f'],
 ['a', 'd', 'g'],
 ['a', 'e', 'f'],
 ['a', 'e', 'g'],
 ['b', 'd', 'f'],
 ['b', 'd', 'g'],
 ['b', 'e', 'f'],
 ['b', 'e', 'g'],
 ['c', 'd', 'f'],
 ['c', 'd', 'g'],
 ['c', 'e', 'f'],
 ['c', 'e', 'g']]

We can also use itertools module to generate the permutation combinations.

Upvotes: 0

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