New exercise ✨: Knapsack

CONTRIBUTING.md

@@ -74,6 +74,8 @@ If there is no such issue, you may open one. The baseline of work is as follows:
 1. Create a `<slug>.test.ts` test file. Here add the tests, per canonical data if possible (more on canonical data below).
 1. Create a `.meta/proof.ci.ts` file. Place a working implementation, assuming it's renamed to `<slug>.ts`
 1. Create `.meta/tests.toml`. If the exercise that is being implemented has test data in the [problem specifications repository][problem-specifications], the contents of this file **must** be a list of UUIDs of the tests that are implemented or not implemented. Scroll down to [tools](#tools) to find the configlet application which aids generating this file _interactively_.
+1. Create a `.meta/config.json`. Copy the structure from any other `.meta/config.json`. Fill the `blurb`, `source` and `source_url` according to the `metadata.yml` in the [problem specifications repository][problem-specifications]. Add yourself as author.
+1. Create a `.docs/instructions.md` file. Copy the instructions from the [problem specifications repository][problem-specifications]
 1. Run the tests locally, using `scripts/test`: `ASSIGNMENT=slug yarn babel-node scripts/test`.
 1. Run the linter locally, using `scripts/lint`: `ASSIGNMENT=slug yarn babel-node scripts/lint`.
 1. Create an entry in `config.json`: a unique _new_ UUID (you can use the `configlet uuid` tool to generate one, scroll down to [tools](#tools) to see how you can get it), give it a difficulty (should be similar to similar exercises), and make sure the _order_ of the file is sane. Currently the file is ordered first on core - non core, then on difficulty low to high, and finally lexographically.

config.json

@@ -964,24 +964,6 @@
           "math"
         ]
       },
-      {
-        "slug": "crypto-square",
-        "name": "Crypto Square",
-        "uuid": "e92b7444-a5c3-4452-82fd-8c70cf14085a",
-        "practices": [],
-        "prerequisites": [],
-        "difficulty": 9,
-        "topics": [
-          "algorithms",
-          "arrays",
-          "conditionals",
-          "loops",
-          "regular_expressions",
-          "sorting",
-          "text_formatting",
-          "transforming"
-        ]
-      },
       {
         "slug": "robot-simulator",
         "name": "Robot Simulator",
@@ -998,21 +980,7 @@
           "strings"
         ]
       },
-      {
-        "slug": "kindergarten-garden",
-        "name": "Kindergarten Garden",
-        "uuid": "d70d3579-999c-452c-9243-98908e24b47e",
-        "practices": [],
-        "prerequisites": [],
-        "difficulty": 7,
-        "topics": [
-          "arrays",
-          "conditionals",
-          "loops",
-          "strings",
-          "text_formatting"
-        ]
-      },
+
       {
         "slug": "armstrong-numbers",
         "name": "Armstrong Numbers",
@@ -1117,6 +1085,21 @@
         "difficulty": 7,
         "topics": ["algorithms", "arrays", "games"]
       },
+      {
+        "slug": "kindergarten-garden",
+        "name": "Kindergarten Garden",
+        "uuid": "d70d3579-999c-452c-9243-98908e24b47e",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 7,
+        "topics": [
+          "arrays",
+          "conditionals",
+          "loops",
+          "strings",
+          "text_formatting"
+        ]
+      },
       {
         "slug": "queen-attack",
         "name": "Queen Attack",
@@ -1142,6 +1125,33 @@
         "prerequisites": [],
         "difficulty": 8,
         "topics": ["algorithms", "closures", "reactive_programming"]
+      },
+      {
+        "slug": "crypto-square",
+        "name": "Crypto Square",
+        "uuid": "e92b7444-a5c3-4452-82fd-8c70cf14085a",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 9,
+        "topics": [
+          "algorithms",
+          "arrays",
+          "conditionals",
+          "loops",
+          "regular_expressions",
+          "sorting",
+          "text_formatting",
+          "transforming"
+        ]
+      },
+      {
+        "slug": "knapsack",
+        "name": "Knapsack",
+        "uuid": "b80ebb8d-9416-4fc8-91ee-3db99411810c",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 9,
+        "topics": ["algorithms"]
       }
     ]
   },

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

@@ -0,0 +1,37 @@
+# Description
+
+In this exercise, let's try to solve a classic problem.
+
+Bob is a thief. After months of careful planning, he finally manages to
+crack the security systems of a high-class apartment.
+
+In front of him are many items, each with a value (v) and weight (w). Bob,
+of course, wants to maximize the total value he can get; he would gladly
+take all of the items if he could. However, to his horror, he realizes that
+the knapsack he carries with him can only hold so much weight (W).
+
+Given a knapsack with a specific carrying capacity (W), help Bob determine
+the maximum value he can get from the items in the house. Note that Bob can
+take only one of each item.
+
+All values given will be strictly positive. Items will be represented as a
+list of pairs, `wi` and `vi`, where the first element `wi` is the weight of
+the *i*th item and `vi` is the value for that item.
+
+For example:
+
+Items: [
+{ "weight": 5, "value": 10 },
+{ "weight": 4, "value": 40 },
+{ "weight": 6, "value": 30 },
+{ "weight": 4, "value": 50 }
+]
+
+Knapsack Limit: 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/.eslintignore

@@ -0,0 +1,12 @@
+!.meta
+
+# Protected or generated
+.git
+.vscode
+
+# When using npm
+node_modules/*
+
+# Configuration files
+babel.config.js
+jest.config.js

exercises/practice/knapsack/.eslintrc

@@ -0,0 +1,23 @@
+{
+  "root": true,
+  "parser": "@typescript-eslint/parser",
+  "parserOptions": {
+    "project": "./tsconfig.json",
+    "ecmaFeatures": {
+      "jsx": true
+    },
+    "ecmaVersion": 2020,
+    "sourceType": "module"
+  },
+  "extends": "@exercism/eslint-config-typescript",
+  "env": {
+    "jest": true
+  },
+  "overrides": [
+    {
+      "files": [".meta/proof.ci.ts", ".meta/exemplar.ts", "*.test.ts"],
+      "excludedFiles": ["custom.test.ts"],
+      "extends": "@exercism/eslint-config-typescript/maintainers"
+    }
+  ]
+}

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

@@ -0,0 +1,12 @@
+{
+  "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.",
+  "authors": ["JoshiRaez"],
+  "contributors": ["SleeplessByte"],
+  "files": {
+    "solution": ["knapsack.ts"],
+    "test": ["knapsack.test.ts"],
+    "example": [".meta/proof.ci.ts"]
+  },
+  "source": "Wikipedia",
+  "source_url": "https://en.wikipedia.org/wiki/Knapsack_problem"
+}

exercises/practice/knapsack/.meta/proof.ci.ts

@@ -0,0 +1,86 @@
+type Item = {
+  weight: number
+  value: number
+}
+
+export function maximumValue({
+  maximumWeight,
+  items,
+}: {
+  maximumWeight: number
+  items: Item[]
+}): number {
+  const maxValueForItemsSizeToWeight: number[][] = new Array(items.length + 1)
+    .fill(undefined)
+    .map(() => new Array(maximumWeight + 1))
+
+  return solve(items.length, maximumWeight, items, maxValueForItemsSizeToWeight)
+}
+
+function solve(
+  setItemsSize: number,
+  maxWeight: number,
+  items: Item[],
+  maxValueForItemsSizeToWeight: number[][]
+): number {
+  return memoizedMax(
+    setItemsSize,
+    maxWeight,
+    items,
+    maxValueForItemsSizeToWeight
+  )
+}
+
+function memoizedMax(
+  setItemsSize: number,
+  maxWeight: number,
+  items: Item[],
+  maxValueForItemsSizeToWeight: number[][]
+): number {
+  const alreadyKnownMaxValue =
+    maxValueForItemsSizeToWeight[setItemsSize][maxWeight]
+  if (alreadyKnownMaxValue || alreadyKnownMaxValue === 0)
+    return alreadyKnownMaxValue
+
+  const max = calculateMax(
+    setItemsSize,
+    maxWeight,
+    items,
+    maxValueForItemsSizeToWeight
+  )
+  maxValueForItemsSizeToWeight[setItemsSize][maxWeight] = max
+
+  return max
+}
+
+function calculateMax(
+  setItemsSize: number,
+  maxWeight: number,
+  items: Item[],
+  maxValueForItemsSizeToWeight: number[][]
+): number {
+  if (!setItemsSize) return 0
+
+  return Math.max(
+    ...Array.from(Array(maxWeight + 1).keys()).map(
+      (checkingWeight) =>
+        memoizedMax(
+          setItemsSize - 1,
+          checkingWeight,
+          items,
+          maxValueForItemsSizeToWeight
+        ) +
+        valueOfItemIfFits(maxWeight, checkingWeight, items[setItemsSize - 1])
+    )
+  )
+}
+
+function valueOfItemIfFits(
+  maxWeight: number,
+  alreadyInBagWeight: number,
+  itemToFit: Item
+): number {
+  if (alreadyInBagWeight + itemToFit.weight <= maxWeight) return itemToFit.value
+
+  return 0
+}

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

@@ -0,0 +1,27 @@
+[a4d7d2f0-ad8a-460c-86f3-88ba709d41a7]
+description = "No items"
+include = true
+
+[1d39e98c-6249-4a8b-912f-87cb12e506b0]
+description = "One item, but too heavy"
+include = true
+
+[833ea310-6323-44f2-9d27-a278740ffbd8]
+description = "Five items. Can\'t be greedy by weight"
+include = true
+
+[277cdc52-f835-4c7d-872b-bff17bab2456]
+description = "Five items. Can\'t be greedy by value"
+include = true
+
+[81d8e679-442b-4f7a-8a59-7278083916c9]
+description = "Example knapsack"
+include = true
+
+[f23a2449-d67c-4c26-bf3e-cde020f27ecc]
+description = "8 items"
+include = true
+
+[7c682ae9-c385-4241-a197-d2fa02c81a11]
+description = "15 items"
+include = true

exercises/practice/knapsack/babel.config.js

@@ -0,0 +1,20 @@
+module.exports = {
+  presets: [
+    [
+      '@babel/preset-env',
+      {
+        targets: {
+          node: 'current',
+        },
+        useBuiltIns: 'entry',
+        corejs: '3.17',
+      },
+    ],
+    '@babel/preset-typescript',
+  ],
+  plugins: [
+    '@babel/proposal-class-properties',
+    '@babel/proposal-object-rest-spread',
+    '@babel/plugin-syntax-bigint',
+  ],
+}

exercises/practice/knapsack/jest.config.js

@@ -0,0 +1,19 @@
+module.exports = {
+  verbose: true,
+  projects: ['<rootDir>'],
+  testMatch: [
+    '**/__tests__/**/*.[jt]s?(x)',
+    '**/test/**/*.[jt]s?(x)',
+    '**/?(*.)+(spec|test).[jt]s?(x)',
+  ],
+  testPathIgnorePatterns: [
+    '/(?:production_)?node_modules/',
+    '.d.ts$',
+    '<rootDir>/test/fixtures',
+    '<rootDir>/test/helpers',
+    '__mocks__',
+  ],
+  transform: {
+    '^.+\\.[jt]sx?$': 'babel-jest',
+  },
+}