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* Retranslate the complete English edition from Simplified Chinese * Polish three English explanations after reader-focused review
47 lines
1.3 KiB
Python
47 lines
1.3 KiB
Python
"""
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File: fractional_knapsack.py
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Created Time: 2023-07-19
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Author: krahets (krahets@163.com)
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"""
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class Item:
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"""Item"""
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def __init__(self, w: int, v: int):
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self.w = w # Item weight
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self.v = v # Item value
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def fractional_knapsack(wgt: list[int], val: list[int], cap: int) -> int:
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"""Fractional knapsack: greedy algorithm"""
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# Create a list of items, each with two attributes: weight and value
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items = [Item(w, v) for w, v in zip(wgt, val)]
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# Sort by value per unit weight, item.v / item.w, in descending order
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items.sort(key=lambda item: item.v / item.w, reverse=True)
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# Repeatedly make greedy choices
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res = 0
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for item in items:
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if item.w <= cap:
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# If enough capacity remains, put the entire current item in the knapsack
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res += item.v
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cap -= item.w
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else:
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# If the remaining capacity is insufficient, put part of the current item in the knapsack
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res += (item.v / item.w) * cap
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# No capacity remains, so exit the loop
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break
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return res
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"""Driver code"""
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if __name__ == "__main__":
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wgt = [10, 20, 30, 40, 50]
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val = [50, 120, 150, 210, 240]
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cap = 50
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n = len(wgt)
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# Greedy algorithm
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res = fractional_knapsack(wgt, val, cap)
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print(f"Maximum total value within the knapsack capacity: {res}")
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