Python/greedy_methods/fractional_knapsack.py
2024-10-14 19:00:30 +05:30

54 lines
1.4 KiB
Python

from bisect import bisect
from itertools import accumulate
def frac_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=lambda x: x[0] / x[1], reverse=True)
vl, wt = [i[0] for i in r], [i[1] for i in r]
acc = list(accumulate(wt))
k = bisect(acc, w)
return (
0
if k == 0
else (
sum(vl[:k]) + (w - acc[k - 1]) * (vl[k]) / (wt[k])
if k != n
else sum(vl[:k])
)
)
if __name__ == "__main__":
import doctest
doctest.testmod()