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SleeplessByte
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New exercise ✨: Knapsack (#478)
Co-authored-by: Derk-Jan Karrenbeld <derk-jan+github@karrenbeld.info>
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‎CONTRIBUTING.md

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@@ -74,6 +74,8 @@ If there is no such issue, you may open one. The baseline of work is as follows:
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1. Create a `<slug>.test.ts` test file. Here add the tests, per canonical data if possible (more on canonical data below).
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1. Create a `.meta/proof.ci.ts` file. Place a working implementation, assuming it's renamed to `<slug>.ts`
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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_.
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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.
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1. Create a `.docs/instructions.md` file. Copy the instructions from the [problem specifications repository][problem-specifications]
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1. Run the tests locally, using `scripts/test`: `ASSIGNMENT=slug yarn babel-node scripts/test`.
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1. Run the linter locally, using `scripts/lint`: `ASSIGNMENT=slug yarn babel-node scripts/lint`.
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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

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

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

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# Description
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In this exercise, let's try to solve a classic problem.
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Bob is a thief. After months of careful planning, he finally manages to
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crack the security systems of a high-class apartment.
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In front of him are many items, each with a value (v) and weight (w). Bob,
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of course, wants to maximize the total value he can get; he would gladly
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take all of the items if he could. However, to his horror, he realizes that
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the knapsack he carries with him can only hold so much weight (W).
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Given a knapsack with a specific carrying capacity (W), help Bob determine
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the maximum value he can get from the items in the house. Note that Bob can
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take only one of each item.
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All values given will be strictly positive. Items will be represented as a
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list of pairs, `wi` and `vi`, where the first element `wi` is the weight of
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the *i*th item and `vi` is the value for that item.
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For example:
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Items: [
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{ "weight": 5, "value": 10 },
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{ "weight": 4, "value": 40 },
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{ "weight": 6, "value": 30 },
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{ "weight": 4, "value": 50 }
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]
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Knapsack Limit: 10
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For the above, the first item has weight 5 and value 10, the second item has
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weight 4 and value 40, and so on.
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In this example, Bob should take the second and fourth item to maximize his
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value, which, in this case, is 90. He cannot get more than 90 as his
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knapsack has a weight limit of 10.

‎exercises/practice/knapsack/.eslintignore

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!.meta
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# Protected or generated
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.git
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.vscode
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# When using npm
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node_modules/*
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# Configuration files
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babel.config.js
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jest.config.js

‎exercises/practice/knapsack/.eslintrc

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

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

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

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

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

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

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

‎exercises/practice/knapsack/babel.config.js

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

‎exercises/practice/knapsack/jest.config.js

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

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