pairs_set_dolver.py

def find_sets2(cards):
    ndims, ncards = cards.shape
    all_features = set([0, 1, 2])

    # solutions contain the indices of the cards forming sets
    solutions = []
    # iterate over all pairs
    for idx1, idx2 in itertools.combinations(range(ncards - 1), 2):
        c1, c2 = cards[:, idx1], cards[:, idx2]

        # compute card that would complete the set
        missing = numpy.empty((ndims,), dtype='i')
        for d in range(ndims):
            if c1[d] == c2[d]:
                # same feature on this dimension ->; missing card also has same
                missing[d] = c1[d]
            else:
                # different features -> find third missing feature
                missing[d] = list(all_features - set([c1[d], c2[d]]))[0]

        # look for missing card in the cards array
        where_idx = numpy.flatnonzero(numpy.all(cards[:, idx2 + 1:].T == missing,
                                                axis=1))
        # append to solutions if found
        if len(where_idx) > 0:
            solutions.append((idx1, idx2, where_idx[0] + idx2 + 1))

    return solutions