RosettaCodeData/Task/Knapsack-problem-Bounded/Python/knapsack-problem-bounded-1.py

52 lines
1.8 KiB
Python

from itertools import groupby
from collections import namedtuple
def anyvalidcomb(items, maxwt, val=0, wt=0):
' All combinations below the maxwt '
if not items:
yield [], val, wt
else:
this, *items = items # car, cdr
for n in range(this.number + 1):
w = wt + n * this.weight
if w > maxwt:
break
v = val + n * this.value
this_comb = [this] * n
for comb, value, weight in anyvalidcomb(items, maxwt, v, w):
yield this_comb + comb, value, weight
maxwt = 400
COMB, VAL, WT = range(3)
Item = namedtuple('Items', 'name weight value number')
items = [ Item(*x) for x in
(
("map", 9, 150, 1),
("compass", 13, 35, 1),
("water", 153, 200, 3),
("sandwich", 50, 60, 2),
("glucose", 15, 60, 2),
("tin", 68, 45, 3),
("banana", 27, 60, 3),
("apple", 39, 40, 3),
("cheese", 23, 30, 1),
("beer", 52, 10, 3),
("suntan cream", 11, 70, 1),
("camera", 32, 30, 1),
("t-shirt", 24, 15, 2),
("trousers", 48, 10, 2),
("umbrella", 73, 40, 1),
("waterproof trousers", 42, 70, 1),
("waterproof overclothes", 43, 75, 1),
("note-case", 22, 80, 1),
("sunglasses", 7, 20, 1),
("towel", 18, 12, 2),
("socks", 4, 50, 1),
("book", 30, 10, 2),
) ]
bagged = max( anyvalidcomb(items, maxwt), key=lambda c: (c[VAL], -c[WT])) # max val or min wt if values equal
print("Bagged the following %i items" % len(bagged[COMB]))
print('\n\t'.join('%i off: %s' % (len(list(grp)), item.name) for item, grp in groupby(sorted(bagged[COMB]))))
print("for a total value of %i and a total weight of %i" % bagged[1:])