fractional_knapsack.py

frombisectimportbisect
fromitertoolsimportaccumulate


deffrac_knapsack(vl, wt, w, n):
"""
 >>> frac_knapsack([60, 100, 120], [10, 20, 30], 50, 3)
 240.0
 >>> frac_knapsack([10, 40, 30, 50], [5, 4, 6, 3], 10, 4)
 105.0
 >>> frac_knapsack([10, 40, 30, 50], [5, 4, 6, 3], 8, 4)
 95.0
 >>> frac_knapsack([10, 40, 30, 50], [5, 4, 6], 8, 4)
 60.0
 >>> frac_knapsack([10, 40, 30], [5, 4, 6, 3], 8, 4)
 60.0
 >>> frac_knapsack([10, 40, 30, 50], [5, 4, 6, 3], 0, 4)
 0
 >>> frac_knapsack([10, 40, 30, 50], [5, 4, 6, 3], 8, 0)
 95.0
 >>> frac_knapsack([10, 40, 30, 50], [5, 4, 6, 3], -8, 4)
 0
 >>> frac_knapsack([10, 40, 30, 50], [5, 4, 6, 3], 8, -4)
 95.0
 >>> frac_knapsack([10, 40, 30, 50], [5, 4, 6, 3], 800, 4)
 130
 >>> frac_knapsack([10, 40, 30, 50], [5, 4, 6, 3], 8, 400)
 95.0
 >>> frac_knapsack("ABCD", [5, 4, 6, 3], 8, 400)
 Traceback (most recent call last):
 ...
 TypeError: unsupported operand type(s) for /: 'str' and 'int'
 """

r=sorted(zip(vl, wt), key=lambdax: x[0] /x[1], reverse=True)
vl, wt= [i[0] foriinr], [i[1] foriinr]
acc=list(accumulate(wt))
k=bisect(acc, w)
return (
0
ifk==0
elsesum(vl[:k]) + (w-acc[k-1]) * (vl[k]) / (wt[k])
ifk!=n
elsesum(vl[:k])
 )


if__name__=="__main__":
importdoctest

doctest.testmod()