Warehouses selector

Which N-out-of-M warehouses to select, given the supply costs from each warehouse to each customer, and the number of warehouses to be opened per warehouse group? This tool selects those warehouses that come with minimal supply costs.

This tool evaluates simply all permutations. Selecting 5 out of 50 warehouses (2.1 million permutations) is possible, but selecting 10 out of 40 warehouses (848 million permutations) will cause a run time issue. The number of permutations also depends on warehouse groupings. A case with multi-million permutations requires a more sophisticated algorithm.

INPUT: warehouse-customer supply costs & warehouse groups (semicolon or tab separated; you can copy data from MS Excel into the text area)

a	a	a	a	a	a	a	a	a	a	a	a	b	b	b	b	b	b	b	b
64	49	34	79	97	81	26	97	96	22	12	14	87	32	94	21	43	70	4	85
91	37	1	99	34	38	59	19	47	87	54	79	86	32	46	21	55	17	8	95
84	17	28	63	82	59	37	20	60	96	79	97	64	10	97	10	11	44	12	77
23	13	1	54	28	32	36	32	35	71	56	74	99	12	28	100	7	73	16	22
72	100	72	66	17	78	43	58	78	94	60	59	52	61	70	77	63	86	100	74
40	49	67	71	55	78	41	30	75	34	8	10	49	54	71	78	8	11	24	96
42	86	20	53	92	53	94	13	69	15	64	39	99	6	98	1	100	92	31	82
33	76	78	2	69	22	36	47	99	72	25	23	71	62	43	96	97	79	50	49
90	52	52	35	89	1	81	94	82	89	41	17	39	76	43	46	81	79	7	86
5	60	8	74	54	55	52	31	73	33	10	11	14	20	41	70	7	32	46	28
17	79	49	96	97	14	31	82	61	63	84	44	20	55	50	89	49	49	16	4
2	74	26	90	5	96	84	82	100	16	19	74	87	33	46	78	98	60	54	5
17	5	8	36	58	82	33	50	14	57	87	100	98	61	87	87	39	21	39	52
88	49	3	87	77	14	80	90	63	66	62	12	1	94	64	71	62	36	6	23
9	82	68	85	9	46	80	99	28	55	43	11	17	17	20	33	34	71	36	53
60	18	77	54	93	57	80	45	54	16	7	66	60	72	57	14	91	23	62	70
12	72	67	61	17	93	66	12	49	11	36	70	21	67	27	90	79	36	50	77
70	41	46	89	38	71	9	37	66	33	8	63	73	23	65	69	91	80	98	15
11	28	72	63	7	39	95	14	33	48	100	41	78	23	73	46	4	15	32	60
18	61	62	91	64	28	3	3	36	43	41	55	50	78	97	83	44	87	39	85

The top row specifies the warehouse group, labeled a,b,c,d,e,f, g or j. Warehouses within the same group should sit next to each other: "a a b b c" is valid top row input, "a b c a b" is not.
Next rows contain supply cost for each warehouse-customer-combination. In the example data, supplying the 3rd customer Cust_0003 from the 2nd warehouse WH_02 will cost 17.

INPUT: number of warehouses to open

Warehouse group	a	b	c	d	e	f	g	h	i	j
Number available
Number to open

Select warehouses