From 93f8cf1fe35f86096910244ca9a0f9c55b108429 Mon Sep 17 00:00:00 2001 From: Erik Schierboom Date: Wed, 22 Jan 2025 12:28:58 +0100 Subject: [PATCH] Add `change` exercise --- config.json | 8 ++ .../practice/change/.docs/instructions.md | 8 ++ .../practice/change/.docs/introduction.md | 26 ++++++ exercises/practice/change/.meta/config.json | 19 +++++ exercises/practice/change/.meta/example.R | 32 +++++++ exercises/practice/change/.meta/tests.toml | 49 +++++++++++ exercises/practice/change/change.R | 3 + exercises/practice/change/test_change.R | 85 +++++++++++++++++++ 8 files changed, 230 insertions(+) create mode 100644 exercises/practice/change/.docs/instructions.md create mode 100644 exercises/practice/change/.docs/introduction.md create mode 100644 exercises/practice/change/.meta/config.json create mode 100644 exercises/practice/change/.meta/example.R create mode 100644 exercises/practice/change/.meta/tests.toml create mode 100644 exercises/practice/change/change.R create mode 100644 exercises/practice/change/test_change.R diff --git a/config.json b/config.json index d0e20ac9..281f9138 100644 --- a/config.json +++ b/config.json @@ -880,6 +880,14 @@ "practices": [], "prerequisites": [], "difficulty": 5 + }, + { + "slug": "change", + "name": "Change", + "uuid": "a625e5e9-43cf-4765-bd9a-e41135132258", + "practices": [], + "prerequisites": [], + "difficulty": 6 } ] }, diff --git a/exercises/practice/change/.docs/instructions.md b/exercises/practice/change/.docs/instructions.md new file mode 100644 index 00000000..5887f4cb --- /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 00000000..b4f8308a --- /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 00000000..d37097b3 --- /dev/null +++ b/exercises/practice/change/.meta/config.json @@ -0,0 +1,19 @@ +{ + "authors": [ + "erikschierboom" + ], + "files": { + "solution": [ + "change.R" + ], + "test": [ + "test_change.R" + ], + "example": [ + ".meta/example.R" + ] + }, + "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.R b/exercises/practice/change/.meta/example.R new file mode 100644 index 00000000..e0ae0ba5 --- /dev/null +++ b/exercises/practice/change/.meta/example.R @@ -0,0 +1,32 @@ +find_fewest_coins <- function(coins, target) { + if (target == 0) { + return(c()) + } + + stopifnot(target > 0) + stopifnot(min(coins) <= target) + + min_amount_coins <- rep(NA, target) |> as.list() + + for (amount in 1:target) { + for (coin in coins[coins <= amount]) { + if (amount - coin == 0) { + sub_amount_coins <- c() + } else { + sub_amount_coins <- min_amount_coins[[amount - coin]] + } + if (any(is.na(sub_amount_coins))) next + + amount_coins <- min_amount_coins[[amount]] + if (!any(is.na(amount_coins)) && + length(amount_coins) <= length(sub_amount_coins) + 1) { + next + } + + min_amount_coins[[amount]] <- c(coin, sub_amount_coins) + } + } + + stopifnot(!any(is.na(min_amount_coins[[target]]))) + min_amount_coins[[target]] +} diff --git a/exercises/practice/change/.meta/tests.toml b/exercises/practice/change/.meta/tests.toml new file mode 100644 index 00000000..2d2f44bc --- /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.R b/exercises/practice/change/change.R new file mode 100644 index 00000000..ef9446f8 --- /dev/null +++ b/exercises/practice/change/change.R @@ -0,0 +1,3 @@ +find_fewest_coins <- function(coins, target) { + +} diff --git a/exercises/practice/change/test_change.R b/exercises/practice/change/test_change.R new file mode 100644 index 00000000..70e5de8f --- /dev/null +++ b/exercises/practice/change/test_change.R @@ -0,0 +1,85 @@ +source("./change.R") +library(testthat) + +test_that("Change for 1 cent", { + coins <- c(1, 5, 10, 25) + target <- 1 + expected <- c(1) + expect_equal(find_fewest_coins(coins, target), expected) +}) + +test_that("Single coin change", { + coins <- c(1, 5, 10, 25, 100) + target <- 25 + expected <- c(25) + expect_equal(find_fewest_coins(coins, target), expected) +}) + +test_that("Multiple coin change", { + coins <- c(1, 5, 10, 25, 100) + target <- 15 + expected <- c(5, 10) + expect_equal(find_fewest_coins(coins, target), expected) +}) + +test_that("Change with Lilliputian Coins", { + coins <- c(1, 4, 15, 20, 50) + target <- 23 + expected <- c(4, 4, 15) + expect_equal(find_fewest_coins(coins, target), expected) +}) + +test_that("Change with Lower Elbonia Coins", { + coins <- c(1, 5, 10, 21, 25) + target <- 63 + expected <- c(21, 21, 21) + expect_equal(find_fewest_coins(coins, target), expected) +}) + +test_that("Large target values", { + coins <- c(1, 2, 5, 10, 20, 50, 100) + target <- 999 + expected <- c( + 2, 2, 5, 20, 20, 50, 100, 100, 100, 100, 100, 100, 100, 100, 100 + ) + expect_equal(find_fewest_coins(coins, target), expected) +}) + +test_that("Possible change without unit coins available", { + coins <- c(2, 5, 10, 20, 50) + target <- 21 + expected <- c(2, 2, 2, 5, 10) + expect_equal(find_fewest_coins(coins, target), expected) +}) + +test_that("Another possible change without unit coins available", { + coins <- c(4, 5) + target <- 27 + expected <- c(4, 4, 4, 5, 5, 5) + expect_equal(find_fewest_coins(coins, target), expected) +}) + +test_that("No coins make 0 change", { + coins <- c(1, 5, 10, 21, 25) + target <- 0 + expected <- c() + expect_equal(find_fewest_coins(coins, target), expected) +}) + +test_that("Error testing for change smaller than the smallest of coins", { + coins <- c(5, 10) + target <- 3 + expect_error(find_fewest_coins(coins, target)) +}) + +test_that("Error if no combination can add up to target", { + coins <- c(5, 10) + target <- 94 + expect_error(find_fewest_coins(coins, target)) +}) + +test_that("Cannot find negative change values", { + coins <- c(1, 2, 5) + target <- -5 + expect_error(find_fewest_coins(coins, target)) +})