Add sum of multiples exercise (#556)

Author: TheRealOwenRees

config.json

@@ -622,6 +622,14 @@
         "practices": [],
         "prerequisites": [],
         "difficulty": 4
+      },
+      {
+        "slug": "sum-of-multiples",
+        "name": "Sum of Multiples",
+        "uuid": "e127a984-ebb1-4709-9cc9-a740bceda94c",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 4
       }
     ]
   },

exercises/practice/sum-of-multiples/.docs/instructions.md

@@ -0,0 +1,27 @@
+# Instructions
+
+Your task is to write the code that calculates the energy points that get awarded to players when they complete a level.
+
+The points awarded depend on two things:
+
+- The level (a number) that the player completed.
+- The base value of each magical item collected by the player during that level.
+
+The energy points are awarded according to the following rules:
+
+1. For each magical item, take the base value and find all the multiples of that value that are less than the level number.
+2. Combine the sets of numbers.
+3. Remove any duplicates.
+4. Calculate the sum of all the numbers that are left.
+
+Let's look at an example:
+
+**The player completed level 20 and found two magical items with base values of 3 and 5.**
+
+To calculate the energy points earned by the player, we need to find all the unique multiples of these base values that are less than level 20.
+
+- Multiples of 3 less than 20: `{3, 6, 9, 12, 15, 18}`
+- Multiples of 5 less than 20: `{5, 10, 15}`
+- Combine the sets and remove duplicates: `{3, 5, 6, 9, 10, 12, 15, 18}`
+- Sum the unique multiples: `3 + 5 + 6 + 9 + 10 + 12 + 15 + 18 = 78`
+- Therefore, the player earns **78** energy points for completing level 20 and finding the two magical items with base values of 3 and 5.

exercises/practice/sum-of-multiples/.docs/introduction.md

@@ -0,0 +1,6 @@
+# Introduction
+
+You work for a company that makes an online, fantasy-survival game.
+
+When a player finishes a level, they are awarded energy points.
+The amount of energy awarded depends on which magical items the player found while exploring that level.

exercises/practice/sum-of-multiples/.meta/config.json

@@ -0,0 +1,20 @@
+{
+  "authors": ["therealowenrees"],
+  "files": {
+    "solution": [
+      "sum_of_multiples.ml"
+    ],
+    "test": [
+      "test.ml"
+    ],
+    "example": [
+      ".meta/example.ml"
+    ],
+    "editor": [
+      "sum_of_multiples.mli"
+    ]
+  },
+  "blurb": "Given a number, find the sum of all the multiples of particular numbers up to but not including that number.",
+  "source": "A variation on Problem 1 at Project Euler",
+  "source_url": "https://projecteuler.net/problem=1"
+}

exercises/practice/sum-of-multiples/.meta/example.ml

@@ -0,0 +1,4 @@
+let sum factors limit =
+  List.init (limit - 1) ((+) 1)
+  |> List.filter (fun i -> List.exists (fun f -> f <> 0 && i mod f = 0) factors)
+  |> List.fold_left ( + ) 0

exercises/practice/sum-of-multiples/.meta/tests.toml

@@ -0,0 +1,58 @@
+# 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.
+
+[54aaab5a-ce86-4edc-8b40-d3ab2400a279]
+description = "no multiples within limit"
+
+[361e4e50-c89b-4f60-95ef-5bc5c595490a]
+description = "one factor has multiples within limit"
+
+[e644e070-040e-4ae0-9910-93c69fc3f7ce]
+description = "more than one multiple within limit"
+
+[607d6eb9-535c-41ce-91b5-3a61da3fa57f]
+description = "more than one factor with multiples within limit"
+
+[f47e8209-c0c5-4786-b07b-dc273bf86b9b]
+description = "each multiple is only counted once"
+
+[28c4b267-c980-4054-93e9-07723db615ac]
+description = "a much larger limit"
+
+[09c4494d-ff2d-4e0f-8421-f5532821ee12]
+description = "three factors"
+
+[2d0d5faa-f177-4ad6-bde9-ebb865083751]
+description = "factors not relatively prime"
+
+[ece8f2e8-96aa-4166-bbb7-6ce71261e354]
+description = "some pairs of factors relatively prime and some not"
+
+[624fdade-6ffb-400e-8472-456a38c171c0]
+description = "one factor is a multiple of another"
+
+[949ee7eb-db51-479c-b5cb-4a22b40ac057]
+description = "much larger factors"
+
+[41093673-acbd-482c-ab80-d00a0cbedecd]
+description = "all numbers are multiples of 1"
+
+[1730453b-baaa-438e-a9c2-d754497b2a76]
+description = "no factors means an empty sum"
+
+[214a01e9-f4bf-45bb-80f1-1dce9fbb0310]
+description = "the only multiple of 0 is 0"
+
+[c423ae21-a0cb-4ec7-aeb1-32971af5b510]
+description = "the factor 0 does not affect the sum of multiples of other factors"
+
+[17053ba9-112f-4ac0-aadb-0519dd836342]
+description = "solutions using include-exclude must extend to cardinality greater than 3"

exercises/practice/sum-of-multiples/Makefile

@@ -0,0 +1,9 @@
+default: clean test
+
+test: 
+	dune runtest
+
+clean:
+	dune clean
+
+.PHONY: clean

exercises/practice/sum-of-multiples/dune

@@ -0,0 +1,20 @@
+(executable
+ (name test)
+ (libraries base ounit2))
+
+(alias
+ (name runtest)
+ (deps
+  (:x test.exe))
+ (action
+  (run %{x})))
+
+(alias
+ (name buildtest)
+ (deps
+  (:x test.exe)))
+
+(env
+ (dev
+  (flags
+   (:standard -warn-error -A))))

exercises/practice/sum-of-multiples/dune-project

@@ -0,0 +1 @@
+(lang dune 1.1)

exercises/practice/sum-of-multiples/sum_of_multiples.ml

@@ -0,0 +1 @@
+let sum _ _ = failwith "'sum' not implemented"