diff --git a/config.json b/config.json index ba3c98c..e6f9cce 100644 --- a/config.json +++ b/config.json @@ -830,6 +830,14 @@ "prerequisites": [], "difficulty": 5 }, + { + "slug": "change", + "name": "Change", + "uuid": "fff0dee7-06d5-4771-8e03-228475204db4", + "practices": [], + "prerequisites": [], + "difficulty": 8 + }, { "slug": "flower-field", "name": "Flower Field", diff --git a/exercises/practice/change/.docs/instructions.md b/exercises/practice/change/.docs/instructions.md new file mode 100644 index 0000000..5887f4c --- /dev/null +++ b/exercises/practice/change/.docs/instructions.md @@ -0,0 +1,8 @@ +# Instructions + +Determine the fewest number of coins to give a customer so that the sum of their values equals the correct amount of change. + +## Examples + +- An amount of 15 with available coin values [1, 5, 10, 25, 100] should return one coin of value 5 and one coin of value 10, or [5, 10]. +- An amount of 40 with available coin values [1, 5, 10, 25, 100] should return one coin of value 5, one coin of value 10, and one coin of value 25, or [5, 10, 25]. diff --git a/exercises/practice/change/.docs/introduction.md b/exercises/practice/change/.docs/introduction.md new file mode 100644 index 0000000..b4f8308 --- /dev/null +++ b/exercises/practice/change/.docs/introduction.md @@ -0,0 +1,26 @@ +# Introduction + +In the mystical village of Coinholt, you stand behind the counter of your bakery, arranging a fresh batch of pastries. +The door creaks open, and in walks Denara, a skilled merchant with a keen eye for quality goods. +After a quick meal, she slides a shimmering coin across the counter, representing a value of 100 units. + +You smile, taking the coin, and glance at the total cost of the meal: 88 units. +That means you need to return 12 units in change. + +Denara holds out her hand expectantly. +"Just give me the fewest coins," she says with a smile. +"My pouch is already full, and I don't want to risk losing them on the road." + +You know you have a few options. +"We have Lumis (worth 10 units), Viras (worth 5 units), and Zenth (worth 2 units) available for change." + +You quickly calculate the possibilities in your head: + +- one Lumis (1 × 10 units) + one Zenth (1 × 2 units) = 2 coins total +- two Viras (2 × 5 units) + one Zenth (1 × 2 units) = 3 coins total +- six Zenth (6 × 2 units) = 6 coins total + +"The best choice is two coins: one Lumis and one Zenth," you say, handing her the change. + +Denara smiles, clearly impressed. +"As always, you've got it right." diff --git a/exercises/practice/change/.meta/config.json b/exercises/practice/change/.meta/config.json new file mode 100644 index 0000000..29e428e --- /dev/null +++ b/exercises/practice/change/.meta/config.json @@ -0,0 +1,19 @@ +{ + "authors": [ + "BNAndras" + ], + "files": { + "solution": [ + "change.coffee" + ], + "test": [ + "change.spec.coffee" + ], + "example": [ + ".meta/example.coffee" + ] + }, + "blurb": "Correctly determine change to be given using the least number of coins.", + "source": "Software Craftsmanship - Coin Change Kata", + "source_url": "https://web.archive.org/web/20130115115225/http://craftsmanship.sv.cmu.edu:80/exercises/coin-change-kata" +} diff --git a/exercises/practice/change/.meta/example.coffee b/exercises/practice/change/.meta/example.coffee new file mode 100644 index 0000000..1372cef --- /dev/null +++ b/exercises/practice/change/.meta/example.coffee @@ -0,0 +1,27 @@ +class Change + @findFewestCoins: (coins, targetBalance) -> + throw new Error "target can't be negative" if targetBalance < 0 + + return [] if targetBalance is 0 + + availableCoins = coins.toSorted() + queue = [0] + visited = {0: []} + + while queue.length > 0 + initialBalance = queue.shift() + + for coin in availableCoins + updatedBalance = initialBalance + coin + continue if updatedBalance > targetBalance or visited[updatedBalance] + + usedCoins = visited[initialBalance].concat coin + if updatedBalance is targetBalance + return usedCoins.toSorted (a, b) -> a - b + + visited[updatedBalance] = usedCoins + queue.push updatedBalance + + throw new Error "can't make target with given coins" + +module.exports = Change diff --git a/exercises/practice/change/.meta/tests.toml b/exercises/practice/change/.meta/tests.toml new file mode 100644 index 0000000..2d2f44b --- /dev/null +++ b/exercises/practice/change/.meta/tests.toml @@ -0,0 +1,49 @@ +# 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. + +[d0ebd0e1-9d27-4609-a654-df5c0ba1d83a] +description = "change for 1 cent" + +[36887bea-7f92-4a9c-b0cc-c0e886b3ecc8] +description = "single coin change" + +[cef21ccc-0811-4e6e-af44-f011e7eab6c6] +description = "multiple coin change" + +[d60952bc-0c1a-4571-bf0c-41be72690cb3] +description = "change with Lilliputian Coins" + +[408390b9-fafa-4bb9-b608-ffe6036edb6c] +description = "change with Lower Elbonia Coins" + +[7421a4cb-1c48-4bf9-99c7-7f049689132f] +description = "large target values" + +[f79d2e9b-0ae3-4d6a-bb58-dc978b0dba28] +description = "possible change without unit coins available" + +[9a166411-d35d-4f7f-a007-6724ac266178] +description = "another possible change without unit coins available" + +[ce0f80d5-51c3-469d-818c-3e69dbd25f75] +description = "a greedy approach is not optimal" + +[bbbcc154-e9e9-4209-a4db-dd6d81ec26bb] +description = "no coins make 0 change" + +[c8b81d5a-49bd-4b61-af73-8ee5383a2ce1] +description = "error testing for change smaller than the smallest of coins" + +[3c43e3e4-63f9-46ac-9476-a67516e98f68] +description = "error if no combination can add up to target" + +[8fe1f076-9b2d-4f44-89fe-8a6ccd63c8f3] +description = "cannot find negative change values" diff --git a/exercises/practice/change/change.coffee b/exercises/practice/change/change.coffee new file mode 100644 index 0000000..15367ce --- /dev/null +++ b/exercises/practice/change/change.coffee @@ -0,0 +1,4 @@ +class Change + @findFewestCoins: (coins, target) -> + +module.exports = Change diff --git a/exercises/practice/change/change.spec.coffee b/exercises/practice/change/change.spec.coffee new file mode 100644 index 0000000..295c466 --- /dev/null +++ b/exercises/practice/change/change.spec.coffee @@ -0,0 +1,59 @@ +Change = require './change' + +describe 'Change', => + it 'change for 1 cent', => + results = Change.findFewestCoins [1, 5, 10, 25], 1 + expect(results).toEqual [1] + + xit 'single coin change', => + results = Change.findFewestCoins [1, 5, 10, 25, 100], 25 + expect(results).toEqual [25] + + xit 'multiple coin change', => + results = Change.findFewestCoins [1, 5, 10, 25, 100], 15 + expect(results).toEqual [5, 10] + + xit 'change with Lilliputian Coins', => + results = Change.findFewestCoins [1, 4, 15, 20, 50], 23 + expect(results).toEqual [4, 4, 15] + + xit 'change with Lower Elbonia Coins', => + results = Change.findFewestCoins [1, 5, 10, 21, 25], 63 + expect(results).toEqual [21, 21, 21] + + xit 'large target values', => + results = Change.findFewestCoins [1, 2, 5, 10, 20, 50, 100], 999 + expect(results).toEqual [ + 2, 2, 5, 20, 20, 50, 100, 100, 100, 100, 100, 100, 100, 100, 100, + ] + + xit 'possible change without unit coins available', => + results = Change.findFewestCoins [2, 5, 10, 20, 50], 21 + expect(results).toEqual [2, 2, 2, 5, 10] + + xit 'another possible change without unit coins available', => + results = Change.findFewestCoins [4, 5], 27 + expect(results).toEqual [4, 4, 4, 5, 5, 5] + + xit 'a greedy approach is not optimal', => + results = Change.findFewestCoins [1, 10, 11], 20 + expect(results).toEqual [10, 10] + + xit 'no coins make 0 change', => + results = Change.findFewestCoins [1, 5, 10, 21, 25], 0 + expect(results).toEqual [] + + xit 'error testing for change smaller than the smallest of coins', => + expect -> + Change.findFewestCoins [5, 10], 3 + .toThrow new Error "can't make target with given coins" + + xit 'error testing if no combination can add up to target', => + expect -> + Change.findFewestCoins [5, 10], 94 + .toThrow new Error "can't make target with given coins" + + xit 'cannot find negative change values', => + expect -> + Change.findFewestCoins [1, 2, 5], -5 + .toThrow new Error "target can't be negative"