From fe865e3af0e914b165fe9bffe67e0e30aa06c36c Mon Sep 17 00:00:00 2001 From: Glenn Jackman Date: Sat, 21 Sep 2024 15:02:15 -0400 Subject: [PATCH] Add knapsack exercise (#346) * Add knapsack exercise * replace a POJO with a static class method --- config.json | 8 ++ .../practice/knapsack/.docs/instructions.md | 25 +++++ .../practice/knapsack/.docs/introduction.md | 8 ++ exercises/practice/knapsack/.meta/config.json | 19 ++++ .../practice/knapsack/.meta/example.coffee | 20 ++++ exercises/practice/knapsack/.meta/tests.toml | 36 +++++++ exercises/practice/knapsack/knapsack.coffee | 4 + .../practice/knapsack/knapsack.spec.coffee | 93 +++++++++++++++++++ 8 files changed, 213 insertions(+) create mode 100644 exercises/practice/knapsack/.docs/instructions.md create mode 100644 exercises/practice/knapsack/.docs/introduction.md create mode 100644 exercises/practice/knapsack/.meta/config.json create mode 100644 exercises/practice/knapsack/.meta/example.coffee create mode 100644 exercises/practice/knapsack/.meta/tests.toml create mode 100644 exercises/practice/knapsack/knapsack.coffee create mode 100644 exercises/practice/knapsack/knapsack.spec.coffee diff --git a/config.json b/config.json index 8154347..20b3b1e 100644 --- a/config.json +++ b/config.json @@ -754,6 +754,14 @@ "practices": [], "prerequisites": [], "difficulty": 5 + }, + { + "slug": "knapsack", + "name": "Knapsack", + "uuid": "a385b861-22a5-4319-9fc0-c0228640ce26", + "practices": [], + "prerequisites": [], + "difficulty": 6 } ] }, diff --git a/exercises/practice/knapsack/.docs/instructions.md b/exercises/practice/knapsack/.docs/instructions.md new file mode 100644 index 0000000..3411db9 --- /dev/null +++ b/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. diff --git a/exercises/practice/knapsack/.docs/introduction.md b/exercises/practice/knapsack/.docs/introduction.md new file mode 100644 index 0000000..9b2bed8 --- /dev/null +++ b/exercises/practice/knapsack/.docs/introduction.md @@ -0,0 +1,8 @@ +# 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. diff --git a/exercises/practice/knapsack/.meta/config.json b/exercises/practice/knapsack/.meta/config.json new file mode 100644 index 0000000..5b1e92a --- /dev/null +++ b/exercises/practice/knapsack/.meta/config.json @@ -0,0 +1,19 @@ +{ + "authors": [ + "glennj" + ], + "files": { + "solution": [ + "knapsack.coffee" + ], + "test": [ + "knapsack.spec.coffee" + ], + "example": [ + ".meta/example.coffee" + ] + }, + "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" +} diff --git a/exercises/practice/knapsack/.meta/example.coffee b/exercises/practice/knapsack/.meta/example.coffee new file mode 100644 index 0000000..9b38dec --- /dev/null +++ b/exercises/practice/knapsack/.meta/example.coffee @@ -0,0 +1,20 @@ +# Algorithm taken from Wikipedia: https://en.wikipedia.org/wiki/Knapsack_problem + +class Knapsack + @maximumValue: ({maximumWeight, items}) -> + return 0 if items.length is 0 + + m = Array.from({length: items.length + 1}, -> new Array(maximumWeight + 1)) + m[0].fill 0 + + for i in [1 .. items.length] + {weight, value} = items[i - 1] + for w in [0 .. maximumWeight] + if weight > w + m[i][w] = m[i - 1][w] + else + m[i][w] = Math.max m[i - 1][w], m[i - 1][w - weight] + value + + m[items.length][maximumWeight] + +module.exports = Knapsack diff --git a/exercises/practice/knapsack/.meta/tests.toml b/exercises/practice/knapsack/.meta/tests.toml new file mode 100644 index 0000000..8e013ef --- /dev/null +++ b/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" diff --git a/exercises/practice/knapsack/knapsack.coffee b/exercises/practice/knapsack/knapsack.coffee new file mode 100644 index 0000000..0234bf6 --- /dev/null +++ b/exercises/practice/knapsack/knapsack.coffee @@ -0,0 +1,4 @@ +class Knapsack + @maximumValue: (args) -> + +module.exports = Knapsack diff --git a/exercises/practice/knapsack/knapsack.spec.coffee b/exercises/practice/knapsack/knapsack.spec.coffee new file mode 100644 index 0000000..5d1bb4b --- /dev/null +++ b/exercises/practice/knapsack/knapsack.spec.coffee @@ -0,0 +1,93 @@ +Knapsack = require './knapsack' + +describe 'Knapsack', -> + it 'no items', -> + input = { + maximumWeight: 100, + items: [] + } + expect(Knapsack.maximumValue input).toEqual 0 + + xit 'one item, too heavy', -> + input = { + maximumWeight: 10, + items: [{ weight: 100, value: 1 }] + } + expect(Knapsack.maximumValue input).toEqual 0 + + xit 'five items (cannot be greedy by weight)', -> + input = { + maximumWeight: 10, + items: [ + { weight: 2, value: 5 }, + { weight: 2, value: 5 }, + { weight: 2, value: 5 }, + { weight: 2, value: 5 }, + { weight: 10, value: 21 } + ] + } + expect(Knapsack.maximumValue input).toEqual 21 + + xit 'five items (cannot be greedy by value)', -> + input = { + maximumWeight: 10, + items: [ + { weight: 2, value: 20 }, + { weight: 2, value: 20 }, + { weight: 2, value: 20 }, + { weight: 2, value: 20 }, + { weight: 10, value: 50 } + ] + } + expect(Knapsack.maximumValue input).toEqual 80 + + xit 'example knapsack', -> + input = { + maximumWeight: 10, + items: [ + { weight: 5, value: 10 }, + { weight: 4, value: 40 }, + { weight: 6, value: 30 }, + { weight: 4, value: 50 } + ] + } + expect(Knapsack.maximumValue input).toEqual 90 + + xit '8 items', -> + input = { + maximumWeight: 104, + items: [ + { weight: 25, value: 350 }, + { weight: 35, value: 400 }, + { weight: 45, value: 450 }, + { weight: 5, value: 20 }, + { weight: 25, value: 70 }, + { weight: 3, value: 8 }, + { weight: 2, value: 5 }, + { weight: 2, value: 5 } + ] + } + expect(Knapsack.maximumValue input).toEqual 900 + + xit '15 items', -> + input = { + maximumWeight: 750, + items: [ + { weight: 70, value: 135 }, + { weight: 73, value: 139 }, + { weight: 77, value: 149 }, + { weight: 80, value: 150 }, + { weight: 82, value: 156 }, + { weight: 87, value: 163 }, + { weight: 90, value: 173 }, + { weight: 94, value: 184 }, + { weight: 98, value: 192 }, + { weight: 106, value: 201 }, + { weight: 110, value: 210 }, + { weight: 113, value: 214 }, + { weight: 115, value: 221 }, + { weight: 118, value: 229 }, + { weight: 120, value: 240 } + ] + } + expect(Knapsack.maximumValue input).toEqual 1458