Add change exercise (#136)

config.json

@@ -714,6 +714,14 @@
         "prerequisites": [],
         "difficulty": 8
       },
+      {
+        "slug": "change",
+        "name": "Change",
+        "uuid": "58e7ebd6-e458-4715-bd05-ba6a35ba0573",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 8
+      },
       {
         "slug": "run-length-encoding",
         "name": "Run-Length Encoding",

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].

exercises/practice/change/.docs/introduction.md

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+# 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."

exercises/practice/change/.meta/config.json

@@ -0,0 +1,19 @@
+{
+  "authors": [
+    "erikschierboom"
+  ],
+  "files": {
+    "solution": [
+      "change.ua"
+    ],
+    "test": [
+      "tests.ua"
+    ],
+    "example": [
+      ".meta/example.ua"
+    ]
+  },
+  "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"
+}

exercises/practice/change/.meta/example.ua

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+ShouldUpdate ← ⨬(>+1∩(⨬(⧻|∘)≍∞.)|0) ≍∞.
+Update       ← ⍜(⊡|□◌) ⊃(⋅⋅∘|⋅⋅⋅⋅∘|⊂⊙⋅⋅∘)
+Process ← (
+  ⊙⊙◌◡⊃(°□⊡⊙⋅⋅|°□⊡⋅⊙⋅)◡(⌵-)°⊟
+  ◡ShouldUpdate
+  ⨬(⋅⋅⋅⋅∘|Update)
+)
+Amounts      ← ⍜(⊢|□[]◌) ↯[+1]:∞
+Combinations ← ▽⊸≡(≤°⊟)/⊂⊞⊂ ⊃(+1⇡◌|∘|⋅Amounts)
+Coins ← (
+  ◇⍆⊣ ∧Process Combinations
+  ⨬(∘|⍤"can't make target with given coins")=∞.
+)
+Change ← ⨬(⍤"target can't be negative"|[]|Coins)+1±,

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"

exercises/practice/change/change.ua

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+# Determine the fewest number of coins for a given target value
+# Change ? Coins Target
+Change ← |2 ⊙⋅(⍤ "Please implement Change" 0)

exercises/practice/change/tests.ua

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+~ "change.ua" ~ Change
+
+# Change for 1 cent
+Coins    ← [1 5 10 25]
+Target   ← 1
+Expected ← [1]
+⍤⤙≍ Expected Change Coins Target
+
+# Single coin change
+Coins    ← [1 5 10 25 100]
+Target   ← 25
+Expected ← [25]
+⍤⤙≍ Expected Change Coins Target
+
+# Multiple coin change
+Coins    ← [1 5 10 25 100]
+Target   ← 15
+Expected ← [5 10]
+⍤⤙≍ Expected Change Coins Target
+
+# Change with Lilliputian Coins
+Coins    ← [1 4 15 20 50]
+Target   ← 23
+Expected ← [4 4 15]
+⍤⤙≍ Expected Change Coins Target
+
+# Change with Lower Elbonia Coins
+Coins    ← [1 5 10 21 25]
+Target   ← 63
+Expected ← [21 21 21]
+⍤⤙≍ Expected Change Coins Target
+
+# Large target values
+Coins    ← [1 2 5 10 20 50 100]
+Target   ← 999
+Expected ← [2 2 5 20 20 50 100 100 100 100 100 100 100 100 100]
+⍤⤙≍ Expected Change Coins Target
+
+# Possible change without unit coins available
+Coins    ← [2 5 10 20 50]
+Target   ← 21
+Expected ← [2 2 2 5 10]
+⍤⤙≍ Expected Change Coins Target
+
+# Another possible change without unit coins available
+Coins    ← [4 5]
+Target   ← 27
+Expected ← [4 4 4 5 5 5]
+⍤⤙≍ Expected Change Coins Target
+
+# No coins make 0 change
+Coins    ← [1 5 10 21 25]
+Target   ← 0
+Expected ← []
+⍤⤙≍ Expected Change Coins Target
+
+# Error testing for change smaller than the smallest of coins
+Coins  ← [5 10]
+Target ← 3
+⍤⤙≍ "can't make target with given coins" ⍣(Change Coins Target)
+
+# Error if no combination can add up to target
+Coins  ← [5 10]
+Target ← 94
+⍤⤙≍ "can't make target with given coins" ⍣(Change Coins Target)
+
+# Cannot find negative change values
+Coins  ← [1 2 5]
+Target ← ¯5
+⍤⤙≍ "target can't be negative" ⍣(Change Coins Target)