feat: Add pythagorean-triplet (#171)

* feat: Add pythagorean-triplet

* Remove comma from config.json

* pythagorean-triplet review feedback

config.json

@@ -97,6 +97,14 @@
         "prerequisites": [],
         "difficulty": 1
       },
+      {
+        "slug": "pythagorean-triplet",
+        "name": "Pythagorean Triplet",
+        "uuid": "915e4694-fb02-496e-9860-001d2aae70cd",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 3
+      },
       {
         "slug": "pop-count",
         "name": "Eliud's Eggs",

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/config.json

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

exercises/practice/pythagorean-triplet/.meta/example.v

@@ -0,0 +1,24 @@
+module main
+
+fn triplets_with_sum(n int) [][]int {
+	mut result := [][]int{}
+	if n < 2 {
+		return result
+	}
+	mut a := 0
+	for {
+		a++
+		numerator := n * (n - 2 * a)
+		denominator := 2 * (n - a)
+		b := numerator / denominator
+		if b < a {
+			break
+		}
+		if numerator % denominator != 0 {
+			continue
+		}
+		c := n - a - b
+		result << [a, b, c]
+	}
+	return result
+}

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

@@ -0,0 +1,24 @@
+# This is an auto-generated file. Regular comments will be removed when this
+# file is regenerated. Regenerating will not touch any manually added keys,
+# so comments can be added in 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/pythagorean-triplet.v

@@ -0,0 +1,4 @@
+module main
+
+fn triplets_with_sum(n int) [][]int {
+}

exercises/practice/pythagorean-triplet/run_test.v

@@ -0,0 +1,60 @@
+module main
+
+fn test_triplets_whose_sum_is_12() {
+	expected := [
+		[3, 4, 5],
+	]
+	assert triplets_with_sum(12) == expected
+}
+
+fn test_triplets_whose_sum_is_108() {
+	expected := [
+		[27, 36, 45],
+	]
+	assert triplets_with_sum(108) == expected
+}
+
+fn test_triplets_whose_sum_is_1000() {
+	expected := [
+		[200, 375, 425],
+	]
+	assert triplets_with_sum(1000) == expected
+}
+
+fn test_no_matching_triplets_for_1001() {
+	expected := [][]int{}
+	assert triplets_with_sum(1001) == expected
+}
+
+fn test_returns_all_matching_triplets() {
+	expected := [
+		[9, 40, 41],
+		[15, 36, 39],
+	]
+	assert triplets_with_sum(90) == expected
+}
+
+fn test_several_matching_triplets() {
+	expected := [
+		[40, 399, 401],
+		[56, 390, 394],
+		[105, 360, 375],
+		[120, 350, 370],
+		[140, 336, 364],
+		[168, 315, 357],
+		[210, 280, 350],
+		[240, 252, 348],
+	]
+	assert triplets_with_sum(840) == expected
+}
+
+fn test_triplets_for_large_number() {
+	expected := [
+		[1200, 14375, 14425],
+		[1875, 14000, 14125],
+		[5000, 12000, 13000],
+		[6000, 11250, 12750],
+		[7500, 10000, 12500],
+	]
+	assert triplets_with_sum(30000) == expected
+}