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https://github.com/onyx-and-iris/grokking-algorithms.git
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73 lines
1.8 KiB
Python
73 lines
1.8 KiB
Python
import logging
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from dataclasses import dataclass
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from tabulate import tabulate
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logging.basicConfig(
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level=logging.DEBUG,
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format="%(asctime)s %(levelname)s\n\r%(message)s",
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datefmt="%H:%M:%S",
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)
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logger = logging.getLogger(__name__)
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@dataclass
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class Item:
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name: str
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value: int
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weight: int
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def dynamic(items, n):
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# create table and zero fill it (required for calculations)
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table = [[0 for _ in range(W + 1)] for _ in range(n + 1)]
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# calculate all possible max values for items in knapsack
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for i in range(1, n + 1):
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for w in range(1, W + 1):
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if items[i - 1].weight <= w:
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table[i][w] = max(
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items[i - 1].value + table[i - 1][w - items[i - 1].weight],
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table[i - 1][w],
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)
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else:
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table[i][w] = table[i - 1][w]
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format_and_print(table)
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return table[-1][-1]
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def format_and_print(table):
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# enumerate first row (headings) + label each row in column0
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for i, row in enumerate(table):
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if i == 0:
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continue
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row[0] = items[i - 1].name
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table[0] = [None, *[i for i in range(1, W + 1)]]
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# print tabularised 2D array
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logger.info([item.name for item in items])
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logger.info(tabulate(table, tablefmt="pretty"))
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# Where items = Guitar + Stereo + Laptop
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items = [Item("Guitar", 1500, 1), Item("Stereo", 3000, 4), Item("Laptop", 2000, 3)]
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W = 4
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greatest_value = dynamic(items, len(items))
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print(f"Greatest value: {greatest_value}")
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# Where items = Guitar + Stereo + Laptop + Iphone
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items = [
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Item("Guitar", 1500, 1),
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Item("Stereo", 3000, 4),
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Item("Laptop", 2000, 3),
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Item("Iphone", 2000, 1),
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]
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W = 4
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greatest_value_with_iphone = dynamic(items, len(items))
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print(f"Greatest value: {greatest_value_with_iphone}")
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