I have a vector of numbers in numpy. For example :

a = [0,1,2,3]

and I have a list of vectors:

b = [[0,1] , [0,2], [0,3], [1,2], [1,3]]

what is the best solution in Python that allows me to find the missing couple of elements in b? In this case it would be:

c = [2,3]

I would add that it is not important the order of the elements, I only need the missing couple.

A first try

I tried using the capabilities of the sets, that through symmetric_difference it gives the missing elements of a in an element of b:

for j in range(len(b)):
 list(set(b[j]).symmetric_difference(a)

But I do not manage to figure out the end of the algorithm or an alternative way.

CodePudding user response：

You can first create all combinations with itertools.combinations then use difference in set like below: (this works for multi elements)

>>> import itertools

>>> a = [0,1,2,3]
>>> b =  [[0,1] , [0,2], [0,3], [1,3]]
>>> c = itertools.combinations(a,2)

>>> res = set(c).difference(map(tuple, b))
>>> list(map(list, res))
[[2, 3], [1, 2]]

# for more explanation
>>> set(itertools.combinations(a,2))
{(0, 1), (0, 2), (0, 3), (1, 2), (1, 3), (2, 3)}