add knapsack

include pipenv files

Pipfile

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+[[source]]
+url = "https://pypi.org/simple"
+verify_ssl = true
+name = "pypi"
+
+[packages]
+tabulate = "*"
+
+[dev-packages]
+
+[requires]
+python_version = "3.11"

Pipfile.lock

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+{
+    "_meta": {
+        "hash": {
+            "sha256": "5b2e934e1ca40f369f7dcd74ed36744eae3116276796320e2800026566302307"
+        },
+        "pipfile-spec": 6,
+        "requires": {
+            "python_version": "3.11"
+        },
+        "sources": [
+            {
+                "name": "pypi",
+                "url": "https://pypi.org/simple",
+                "verify_ssl": true
+            }
+        ]
+    },
+    "default": {
+        "tabulate": {
+            "hashes": [
+                "sha256:0095b12bf5966de529c0feb1fa08671671b3368eec77d7ef7ab114be2c068b3c",
+                "sha256:024ca478df22e9340661486f85298cff5f6dcdba14f3813e8830015b9ed1948f"
+            ],
+            "index": "pypi",
+            "markers": "python_version >= '3.7'",
+            "version": "==0.9.0"
+        }
+    },
+    "develop": {}
+}

chapter11/knapsack.py

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