From 00e102add42157f7bfc199d0c232aa4e050911b3 Mon Sep 17 00:00:00 2001
From: Erik Schierboom <erik_schierboom@hotmail.com>
Date: Fri, 18 Oct 2024 09:58:59 +0200
Subject: [PATCH] Add `nth-prime` exercise

---
 config.json                                   |  8 ++++++
 .../practice/nth-prime/.docs/instructions.md  |  7 ++++++
 .../practice/nth-prime/.meta/config.json      | 19 ++++++++++++++
 exercises/practice/nth-prime/.meta/example.R  | 23 +++++++++++++++++
 exercises/practice/nth-prime/.meta/tests.toml | 25 +++++++++++++++++++
 exercises/practice/nth-prime/nth-prime.R      |  3 +++
 exercises/practice/nth-prime/test_nth-prime.R | 22 ++++++++++++++++
 7 files changed, 107 insertions(+)
 create mode 100644 exercises/practice/nth-prime/.docs/instructions.md
 create mode 100644 exercises/practice/nth-prime/.meta/config.json
 create mode 100644 exercises/practice/nth-prime/.meta/example.R
 create mode 100644 exercises/practice/nth-prime/.meta/tests.toml
 create mode 100644 exercises/practice/nth-prime/nth-prime.R
 create mode 100644 exercises/practice/nth-prime/test_nth-prime.R

diff --git a/config.json b/config.json
index 2c990de2..0ea6909a 100644
--- a/config.json
+++ b/config.json
@@ -848,6 +848,14 @@
         "practices": [],
         "prerequisites": [],
         "difficulty": 4
+      },
+      {
+        "slug": "nth-prime",
+        "name": "Nth Prime",
+        "uuid": "e61c707d-eb0d-4c37-8c0f-014db4504d3d",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 5
       }
     ]
   },
diff --git a/exercises/practice/nth-prime/.docs/instructions.md b/exercises/practice/nth-prime/.docs/instructions.md
new file mode 100644
index 00000000..065e323a
--- /dev/null
+++ b/exercises/practice/nth-prime/.docs/instructions.md
@@ -0,0 +1,7 @@
+# Instructions
+
+Given a number n, determine what the nth prime is.
+
+By listing the first six prime numbers: 2, 3, 5, 7, 11, and 13, we can see that the 6th prime is 13.
+
+If your language provides methods in the standard library to deal with prime numbers, pretend they don't exist and implement them yourself.
diff --git a/exercises/practice/nth-prime/.meta/config.json b/exercises/practice/nth-prime/.meta/config.json
new file mode 100644
index 00000000..76301631
--- /dev/null
+++ b/exercises/practice/nth-prime/.meta/config.json
@@ -0,0 +1,19 @@
+{
+  "authors": [
+    "erikschierboom"
+  ],
+  "files": {
+    "solution": [
+      "nth-prime.R"
+    ],
+    "test": [
+      "test_nth-prime.R"
+    ],
+    "example": [
+      ".meta/example.R"
+    ]
+  },
+  "blurb": "Given a number n, determine what the nth prime is.",
+  "source": "A variation on Problem 7 at Project Euler",
+  "source_url": "https://projecteuler.net/problem=7"
+}
diff --git a/exercises/practice/nth-prime/.meta/example.R b/exercises/practice/nth-prime/.meta/example.R
new file mode 100644
index 00000000..18210734
--- /dev/null
+++ b/exercises/practice/nth-prime/.meta/example.R
@@ -0,0 +1,23 @@
+prime <- function(n) {
+  stopifnot(n > 0)
+
+  primes <- c(2, 3)
+  current <- 6
+
+  while (length(primes) < n) {
+    limit <- sqrt(current + 1)
+    prime_check <- primes[primes <= limit]
+
+    if (all((current - 1) %% prime_check != 0)) {
+      primes <- c(primes, current - 1)
+    }
+
+    if (all((current + 1) %% prime_check != 0)) {
+      primes <- c(primes, current + 1)
+    }
+
+    current <- current + 6
+  }
+
+  primes[n]
+}
diff --git a/exercises/practice/nth-prime/.meta/tests.toml b/exercises/practice/nth-prime/.meta/tests.toml
new file mode 100644
index 00000000..daccec42
--- /dev/null
+++ b/exercises/practice/nth-prime/.meta/tests.toml
@@ -0,0 +1,25 @@
+# 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.
+
+[75c65189-8aef-471a-81de-0a90c728160c]
+description = "first prime"
+
+[2c38804c-295f-4701-b728-56dea34fd1a0]
+description = "second prime"
+
+[56692534-781e-4e8c-b1f9-3e82c1640259]
+description = "sixth prime"
+
+[fce1e979-0edb-412d-93aa-2c744e8f50ff]
+description = "big prime"
+
+[bd0a9eae-6df7-485b-a144-80e13c7d55b2]
+description = "there is no zeroth prime"
diff --git a/exercises/practice/nth-prime/nth-prime.R b/exercises/practice/nth-prime/nth-prime.R
new file mode 100644
index 00000000..ccd0dfe3
--- /dev/null
+++ b/exercises/practice/nth-prime/nth-prime.R
@@ -0,0 +1,3 @@
+prime <- function(n) {
+
+}
diff --git a/exercises/practice/nth-prime/test_nth-prime.R b/exercises/practice/nth-prime/test_nth-prime.R
new file mode 100644
index 00000000..8c8862d6
--- /dev/null
+++ b/exercises/practice/nth-prime/test_nth-prime.R
@@ -0,0 +1,22 @@
+source("./nth-prime.R")
+library(testthat)
+
+test_that("First prime", {
+  expect_equal(prime(1), 2)
+})
+
+test_that("Second prime", {
+  expect_equal(prime(2), 3)
+})
+
+test_that("Sixth prime", {
+  expect_equal(prime(6), 13)
+})
+
+test_that("Big prime", {
+  expect_equal(prime(10001), 104743)
+})
+
+test_that("There is no zeroth prime", {
+  expect_error(prime(0))
+})