Add knapsack exercise

config.json

@@ -514,6 +514,14 @@
           "strings"
         ]
       },
+      {
+        "slug": "knapsack",
+        "name": "Knapsack",
+        "uuid": "9d386afd-6d15-4606-98a1-c88894416cda",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 5
+      },
       {
         "slug": "react",
         "name": "React",

exercises/practice/knapsack/.docs/instructions.md

@@ -0,0 +1,25 @@
+# Instructions
+
+Your task is to determine which items to take so that the total value of his selection is maximized, taking into account the knapsack's carrying capacity.
+
+Items will be represented as a list of items.
+Each item will have a weight and value.
+All values given will be strictly positive.
+Bob can take only one of each item.
+
+For example:
+
+```text
+Items: [
+  { "weight": 5, "value": 10 },
+  { "weight": 4, "value": 40 },
+  { "weight": 6, "value": 30 },
+  { "weight": 4, "value": 50 }
+]
+
+Knapsack Maximum Weight: 10
+```
+
+For the above, the first item has weight 5 and value 10, the second item has weight 4 and value 40, and so on.
+In this example, Bob should take the second and fourth item to maximize his value, which, in this case, is 90.
+He cannot get more than 90 as his knapsack has a weight limit of 10.

exercises/practice/knapsack/.docs/introduction.md

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+# Introduction
+
+Bob is a thief.
+After months of careful planning, he finally manages to crack the security systems of a fancy store.
+
+In front of him are many items, each with a value and weight.
+Bob would gladly take all of the items, but his knapsack can only hold so much weight.
+Bob has to carefully consider which items to take so that the total value of his selection is maximized.

exercises/practice/knapsack/.meta/config.json

@@ -0,0 +1,19 @@
+{
+  "authors": [
+    "keiravillekode"
+  ],
+  "files": {
+    "solution": [
+      "source/knapsack.d"
+    ],
+    "test": [
+      "source/knapsack.d"
+    ],
+    "example": [
+      "example/knapsack.d"
+    ]
+  },
+  "blurb": "Given a knapsack that can only carry a certain weight, determine which items to put in the knapsack in order to maximize their combined value.",
+  "source": "Wikipedia",
+  "source_url": "https://en.wikipedia.org/wiki/Knapsack_problem"
+}

exercises/practice/knapsack/.meta/tests.toml

@@ -0,0 +1,36 @@
+# This is an auto-generated file.
+#
+# Regenerating this file via `configlet sync` will:
+# - Recreate every `description` key/value pair
+# - Recreate every `reimplements` key/value pair, where they exist in problem-specifications
+# - Remove any `include = true` key/value pair (an omitted `include` key implies inclusion)
+# - Preserve any other key/value pair
+#
+# As user-added comments (using the # character) will be removed when this file
+# is regenerated, comments can be added via a `comment` key.
+
+[a4d7d2f0-ad8a-460c-86f3-88ba709d41a7]
+description = "no items"
+include = false
+
+[3993a824-c20e-493d-b3c9-ee8a7753ee59]
+description = "no items"
+reimplements = "a4d7d2f0-ad8a-460c-86f3-88ba709d41a7"
+
+[1d39e98c-6249-4a8b-912f-87cb12e506b0]
+description = "one item, too heavy"
+
+[833ea310-6323-44f2-9d27-a278740ffbd8]
+description = "five items (cannot be greedy by weight)"
+
+[277cdc52-f835-4c7d-872b-bff17bab2456]
+description = "five items (cannot be greedy by value)"
+
+[81d8e679-442b-4f7a-8a59-7278083916c9]
+description = "example knapsack"
+
+[f23a2449-d67c-4c26-bf3e-cde020f27ecc]
+description = "8 items"
+
+[7c682ae9-c385-4241-a197-d2fa02c81a11]
+description = "15 items"

exercises/practice/knapsack/dub.sdl

@@ -0,0 +1,2 @@
+name "knapsack"
+buildRequirements "disallowDeprecations"

exercises/practice/knapsack/example/knapsack.d

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+module knapack;
+
+struct Item {
+    uint weight;
+    uint value;
+}
+
+uint maximumValue(Item[] items, uint maximumWeight)
+{
+    auto table = new uint[](maximumWeight + 1);
+    foreach (item; items) {
+        uint index = maximumWeight + 1;
+        while (index > item.weight) {
+            --index;
+            auto value = item.value + table[index - item.weight];
+            if (table[index] < value) {
+                table[index] = value;
+            }
+        }
+    }
+    return table[maximumWeight];
+}

exercises/practice/knapsack/source/knapsack.d

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+module knapsack;
+
+struct Item {
+    uint weight;
+    uint value;
+}
+
+uint maximumValue(Item[] items, uint maximumWeight)
+{
+    // implement this function
+}
+
+unittest
+{
+    immutable int allTestsEnabled = 0;
+
+    // No items
+    {
+        Item[] items = [
+        ];
+        assert(maximumValue(items, 100) == 0);
+    }
+
+    static if (allTestsEnabled)
+    {
+        // One item, too heavy
+        {
+            Item[] items = [
+                Item(weight: 100, value: 1),
+            ];
+            assert(maximumValue(items, 10) == 0);
+        }
+
+        // Five items (cannot be greedy by weight)
+        {
+            Item[] items = [
+                Item(weight: 2, value: 5),
+                Item(weight: 2, value: 5),
+                Item(weight: 2, value: 5),
+                Item(weight: 2, value: 5),
+                Item(weight: 10, value: 21),
+            ];
+            assert(maximumValue(items, 10) == 21);
+        }
+
+        // Five items (cannot be greedy by value)
+        {
+            Item[] items = [
+                Item(weight: 2, value: 20),
+                Item(weight: 2, value: 20),
+                Item(weight: 2, value: 20),
+                Item(weight: 2, value: 20),
+                Item(weight: 10, value: 50),
+            ];
+            assert(maximumValue(items, 10) == 80);
+        }
+
+        // Example knapsack
+        {
+            Item[] items = [
+                Item(weight: 5, value: 10),
+                Item(weight: 4, value: 40),
+                Item(weight: 6, value: 30),
+                Item(weight: 4, value: 50),
+            ];
+            assert(maximumValue(items, 10) == 90);
+        }
+
+        // 8 items
+        {
+            Item[] items = [
+                Item(weight: 25, value: 350),
+                Item(weight: 35, value: 400),
+                Item(weight: 45, value: 450),
+                Item(weight: 5, value: 20),
+                Item(weight: 25, value: 70),
+                Item(weight: 3, value: 8),
+                Item(weight: 2, value: 5),
+                Item(weight: 2, value: 5),
+            ];
+            assert(maximumValue(items, 104) == 900);
+        }
+
+        // 15 items
+        {
+            Item[] items = [
+                Item(weight: 70, value: 135),
+                Item(weight: 73, value: 139),
+                Item(weight: 77, value: 149),
+                Item(weight: 80, value: 150),
+                Item(weight: 82, value: 156),
+                Item(weight: 87, value: 163),
+                Item(weight: 90, value: 173),
+                Item(weight: 94, value: 184),
+                Item(weight: 98, value: 192),
+                Item(weight: 106, value: 201),
+                Item(weight: 110, value: 210),
+                Item(weight: 113, value: 214),
+                Item(weight: 115, value: 221),
+                Item(weight: 118, value: 229),
+                Item(weight: 120, value: 240),
+            ];
+            assert(maximumValue(items, 750) == 1458);
+        }
+    }
+}