✨ Add pythagorean-triplet (#301)

config.json

@@ -581,6 +581,18 @@
         ],
       "difficulty": 1,
       "status": "wip"
+      },
+      {
+        "slug": "pythagorean-triplet",
+        "name": "Pythagorean Triplet",
+        "uuid": "07aae7fe-22b2-4919-83f7-1ee145216dbd",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 3,
+        "status": "active",
+        "topics": [
+          "math"
+        ]
       }
     ]
   },

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 +1,17 @@
+{
+  "authors": [],
+  "files": {
+    "solution": [
+      "pythagorean-triplet.R"
+    ],
+    "test": [
+      "test_pythagorean-triplet.R"
+    ],
+    "example": [
+      ".meta/example.R"
+    ]
+  },
+  "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/example.R

@@ -0,0 +1,12 @@
+pythagorean_triplet <- function(n) {
+  triplets <- list()
+  for (a in 1:n) {
+    for (b in a + 1:n) {
+      c <- n - a - b
+      if (b < c && a^2 + b^2 == c^2) {
+        triplets <- append(triplets, list(c(a, b, c)))
+      }
+    }
+  }
+  triplets
+}

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/pythagorean-triplet.R

@@ -0,0 +1,3 @@
+pythagorean_triplet <- function(n) {
+
+}

exercises/practice/pythagorean-triplet/test_pythagorean-triplet.R

@@ -0,0 +1,51 @@
+source("./pythagorean-triplet.R")
+library(testthat)
+
+test_that("triplets whose sum is 12", {
+  expect_equal(pythagorean_triplet(12), list(3:5))
+})
+
+test_that("triplets whose sum is 108", {
+  expect_equal(pythagorean_triplet(108), list(c(27, 36, 45)))
+})
+
+test_that("triplets whose sum is 1000", {
+  expect_equal(pythagorean_triplet(1000), list(c(200, 375, 425)))
+})
+
+test_that("no matching triplets for 1001", {
+  expect_equal(pythagorean_triplet(1001), list())
+})
+
+test_that("returns all matching triplets", {
+  expect_equal(pythagorean_triplet(90), list(c(9, 40, 41), c(15, 36, 39)))
+})
+
+test_that("several matching triplets", {
+  expect_equal(
+    pythagorean_triplet(840),
+    list(
+      c(40, 399, 401),
+      c(56, 390, 394),
+      c(105, 360, 375),
+      c(120, 350, 370),
+      c(140, 336, 364),
+      c(168, 315, 357),
+      c(210, 280, 350),
+      c(240, 252, 348)
+    )
+  )
+})
+
+test_that("triplets for large number", {
+  expect_equal(
+    pythagorean_triplet(30000),
+    list(
+      c(1200, 14375, 14425),
+      c(1875, 14000, 14125),
+      c(5000, 12000, 13000),
+      c(6000, 11250, 12750),
+      c(7500, 10000, 12500)
+    )
+  )
+})