Add pythagorean-triplet exercise (#143)

* Add pythagorean-triplet exercise
* Return Set Triplet rather than List Triplet to ignore order, as suggested by Isaac

config.json

@@ -395,6 +395,14 @@
         "prerequisites": [],
         "difficulty": 3
       },
+      {
+        "slug": "pythagorean-triplet",
+        "name": "Pythagorean Triplet",
+        "uuid": "0b50a6d7-79fc-46a2-a62c-9d003c815896",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 3
+      },
       {
         "slug": "queen-attack",
         "name": "Queen Attack",

exercises/practice/pythagorean-triplet/.docs/instructions.md

@@ -0,0 +1,23 @@
+# Instructions
+
+A Pythagorean triplet is a set of three natural numbers, {a, b, c}, for which,
+
+```text
+a² + b² = c²
+```
+
+and such that,
+
+```text
+a < b < c
+```
+
+For example,
+
+```text
+3² + 4² = 5².
+```
+
+Given an input integer N, find all Pythagorean triplets for which `a + b + c = N`.
+
+For example, with N = 1000, there is exactly one Pythagorean triplet for which `a + b + c = 1000`: `{200, 375, 425}`.

exercises/practice/pythagorean-triplet/.meta/Example.roc

@@ -0,0 +1,23 @@
+module [tripletsWithSum]
+
+Triplet : (U64, U64, U64)
+
+tripletsWithSum : U64 -> Set Triplet
+tripletsWithSum = \sum ->
+    help = \triplets, a, b ->
+        if a + b + b + 1 > sum then
+            # c would have to be too small (≤ b)
+            if 3 * (a + 1) > sum then
+                # we can't increment a so we're done
+                triplets
+            else
+                help triplets (a + 1) (a + 2) # increment a
+        else
+            c = sum - a - b
+            newTriplets =
+                if a * a + b * b == c * c then
+                    triplets |> List.append (a, b, c) # success!
+                else
+                    triplets
+            help newTriplets a (b + 1) # increment b
+    help [] 1 2 |> Set.fromList

exercises/practice/pythagorean-triplet/.meta/config.json

@@ -0,0 +1,19 @@
+{
+  "authors": [
+    "ageron"
+  ],
+  "files": {
+    "solution": [
+      "PythagoreanTriplet.roc"
+    ],
+    "test": [
+      "pythagorean-triplet-test.roc"
+    ],
+    "example": [
+      ".meta/Example.roc"
+    ]
+  },
+  "blurb": "There exists exactly one Pythagorean triplet for which a + b + c = 1000. Find the triplet.",
+  "source": "Problem 9 at Project Euler",
+  "source_url": "https://projecteuler.net/problem=9"
+}

exercises/practice/pythagorean-triplet/.meta/template.j2

@@ -0,0 +1,16 @@
+{%- import "generator_macros.j2" as macros with context -%}
+{{ macros.canonical_ref() }}
+{{ macros.header() }}
+
+import {{ exercise | to_pascal }} exposing [{{ cases[0]["property"] | to_camel }}]
+
+{% for case in cases -%}
+# {{ case["description"] }}
+expect
+    result = {{ case["property"] | to_camel }} {{ case["input"]["n"] }}
+    expected = Set.fromList [{%- for triplet in case["expected"] %}
+      ({{ triplet[0] }}, {{ triplet[1] }}, {{ triplet[2] }}),
+      {%- endfor %}]
+    result == expected
+
+{% endfor %}

exercises/practice/pythagorean-triplet/.meta/tests.toml

@@ -0,0 +1,31 @@
+# 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.
+
+[a19de65d-35b8-4480-b1af-371d9541e706]
+description = "triplets whose sum is 12"
+
+[48b21332-0a3d-43b2-9a52-90b2a6e5c9f5]
+description = "triplets whose sum is 108"
+
+[dffc1266-418e-4daa-81af-54c3e95c3bb5]
+description = "triplets whose sum is 1000"
+
+[5f86a2d4-6383-4cce-93a5-e4489e79b186]
+description = "no matching triplets for 1001"
+
+[bf17ba80-1596-409a-bb13-343bdb3b2904]
+description = "returns all matching triplets"
+
+[9d8fb5d5-6c6f-42df-9f95-d3165963ac57]
+description = "several matching triplets"
+
+[f5be5734-8aa0-4bd1-99a2-02adcc4402b4]
+description = "triplets for large number"

exercises/practice/pythagorean-triplet/PythagoreanTriplet.roc

@@ -0,0 +1,7 @@
+module [tripletsWithSum]
+
+Triplet : (U64, U64, U64)
+
+tripletsWithSum : U64 -> Set Triplet
+tripletsWithSum = \sum ->
+    crash "Please implement the 'tripletsWithSum' function"

exercises/practice/pythagorean-triplet/pythagorean-triplet-test.roc

@@ -0,0 +1,78 @@
+# These tests are auto-generated with test data from:
+# https://github.com/exercism/problem-specifications/tree/main/exercises/pythagorean-triplet/canonical-data.json
+# File last updated on 2024-10-10
+app [main] {
+    pf: platform "https://github.com/roc-lang/basic-cli/releases/download/0.15.0/SlwdbJ-3GR7uBWQo6zlmYWNYOxnvo8r6YABXD-45UOw.tar.br",
+}
+
+main =
+    Task.ok {}
+
+import PythagoreanTriplet exposing [tripletsWithSum]
+
+# triplets whose sum is 12
+expect
+    result = tripletsWithSum 12
+    expected = Set.fromList [
+        (3, 4, 5),
+    ]
+    result == expected
+
+# triplets whose sum is 108
+expect
+    result = tripletsWithSum 108
+    expected = Set.fromList [
+        (27, 36, 45),
+    ]
+    result == expected
+
+# triplets whose sum is 1000
+expect
+    result = tripletsWithSum 1000
+    expected = Set.fromList [
+        (200, 375, 425),
+    ]
+    result == expected
+
+# no matching triplets for 1001
+expect
+    result = tripletsWithSum 1001
+    expected = Set.fromList []
+    result == expected
+
+# returns all matching triplets
+expect
+    result = tripletsWithSum 90
+    expected = Set.fromList [
+        (9, 40, 41),
+        (15, 36, 39),
+    ]
+    result == expected
+
+# several matching triplets
+expect
+    result = tripletsWithSum 840
+    expected = Set.fromList [
+        (40, 399, 401),
+        (56, 390, 394),
+        (105, 360, 375),
+        (120, 350, 370),
+        (140, 336, 364),
+        (168, 315, 357),
+        (210, 280, 350),
+        (240, 252, 348),
+    ]
+    result == expected
+
+# triplets for large number
+expect
+    result = tripletsWithSum 30000
+    expected = Set.fromList [
+        (1200, 14375, 14425),
+        (1875, 14000, 14125),
+        (5000, 12000, 13000),
+        (6000, 11250, 12750),
+        (7500, 10000, 12500),
+    ]
+    result == expected
+