We need to only consider patterns that have punches in the first row and column. If the first row is empty, the pattern can be shifted up. If the first column is empty, the pattern can be shifted left. In either case, we can derive a similar pattern that we do consider. For these patterns, … Read more
If you want to keep the key:value in the permutations you can use: import itertools keys, values = zip(*my_dict.items()) permutations_dicts = [dict(zip(keys, v)) for v in itertools.product(*values)] this will provide you a list of dicts with the permutations: print(permutations_dicts) [{‘A’:’D’, ‘B’:’F’, ‘C’:’I’}, {‘A’:’D’, ‘B’:’F’, ‘C’:’J’}, … ] Disclaimer: not exactly what the OP was asking, … Read more
Robert Floyd invented a sampling algorithm for just such situations. It’s generally superior to shuffling then grabbing the first x elements since it doesn’t require O(y) storage. As originally written it assumes values from 1..N, but it’s trivial to produce 0..N and/or use non-contiguous values by simply treating the values it produces as subscripts into … Read more
itertools can do this: import itertools for comb in itertools.combinations([1, 2, 3, 4], 3): print(comb) Outputs: (1, 2, 3) (1, 2, 4) (1, 3, 4) (2, 3, 4)
if n is not far from r then using the recursive definition of combination is probably better, since xC0 == 1 you will only have a few iterations: The relevant recursive definition here is: nCr = (n-1)C(r-1) * n/r This can be nicely computed using tail recursion with the following list: [(n – r, 0), … Read more
You could use itertools to iterate through every combination of every possible size, and filter out everything that doesn’t sum to 10: import itertools numbers = [1, 2, 3, 7, 7, 9, 10] target = 10 result = [seq for i in range(len(numbers), 0, -1) for seq in itertools.combinations(numbers, i) if sum(seq) == target] print(result) … Read more
This answer missed one aspect: the OP asked for ALL combinations… not just combinations of length “r”. So you’d either have to loop through all lengths “L”: import itertools stuff = [1, 2, 3] for L in range(len(stuff) + 1): for subset in itertools.combinations(stuff, L): print(subset) Or — if you want to get snazzy (or … Read more