series: add exercise

config.json

@@ -648,6 +648,14 @@
         "prerequisites": [],
         "difficulty": 1,
         "status": "beta"
+      },
+      {
+        "slug": "series",
+        "name": "Series",
+        "uuid": "2ef6f027-a27c-4b00-bf1e-2969baf04a36",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 3
       }
     ]
   },

exercises/practice/series/.docs/instructions.md

@@ -0,0 +1,19 @@
+# Instructions
+
+Given a string of digits, output all the contiguous substrings of length `n` in that string in the order that they appear.
+
+For example, the string "49142" has the following 3-digit series:
+
+- "491"
+- "914"
+- "142"
+
+And the following 4-digit series:
+
+- "4914"
+- "9142"
+
+And if you ask for a 6-digit series from a 5-digit string, you deserve whatever you get.
+
+Note that these series are only required to occupy _adjacent positions_ in the input;
+the digits need not be _numerically consecutive_.

exercises/practice/series/.meta/config.json

@@ -0,0 +1,19 @@
+{
+  "authors": [
+    "erikschierboom"
+  ],
+  "files": {
+    "solution": [
+      "series.R"
+    ],
+    "test": [
+      "test_series.R"
+    ],
+    "example": [
+      ".meta/example.R"
+    ]
+  },
+  "blurb": "Given a string of digits, output all the contiguous substrings of length `n` in that string.",
+  "source": "A subset of the Problem 8 at Project Euler",
+  "source_url": "https://projecteuler.net/problem=8"
+}

exercises/practice/series/.meta/example.R

@@ -0,0 +1,7 @@
+slices <- function(series, slice_length) {
+  stopifnot(nchar(series) > 0 & slice_length %in% 1:nchar(series))
+
+  slice_indices <- 1:(nchar(series) - slice_length + 1)
+  sapply(slice_indices, function(i)
+    substr(series, i, i + slice_length - 1))
+}

exercises/practice/series/.meta/tests.toml

@@ -0,0 +1,43 @@
+# 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.
+
+[7ae7a46a-d992-4c2a-9c15-a112d125ebad]
+description = "slices of one from one"
+
+[3143b71d-f6a5-4221-aeae-619f906244d2]
+description = "slices of one from two"
+
+[dbb68ff5-76c5-4ccd-895a-93dbec6d5805]
+description = "slices of two"
+
+[19bbea47-c987-4e11-a7d1-e103442adf86]
+description = "slices of two overlap"
+
+[8e17148d-ba0a-4007-a07f-d7f87015d84c]
+description = "slices can include duplicates"
+
+[bd5b085e-f612-4f81-97a8-6314258278b0]
+description = "slices of a long series"
+
+[6d235d85-46cf-4fae-9955-14b6efef27cd]
+description = "slice length is too large"
+
+[d7957455-346d-4e47-8e4b-87ed1564c6d7]
+description = "slice length is way too large"
+
+[d34004ad-8765-4c09-8ba1-ada8ce776806]
+description = "slice length cannot be zero"
+
+[10ab822d-8410-470a-a85d-23fbeb549e54]
+description = "slice length cannot be negative"
+
+[c7ed0812-0e4b-4bf3-99c4-28cbbfc246a2]
+description = "empty series is invalid"

exercises/practice/series/series.R

@@ -0,0 +1,3 @@
+slices <- function(series, slice_length) {
+
+}

exercises/practice/series/test_series.R

@@ -0,0 +1,58 @@
+source("./series.R")
+library(testthat)
+
+test_that("Slices of one from one", {
+  expect_equal(slices("1", 1), c("1"))
+})
+
+test_that("Slices of one from two", {
+  expect_equal(slices("12", 1), c("1", "2"))
+})
+
+test_that("Slices of two", {
+  expect_equal(slices("35", 2), c("35"))
+})
+
+test_that("Slices of two overlap", {
+  expect_equal(slices("9142", 2), c("91", "14", "42"))
+})
+
+test_that("Slices can include duplicates", {
+  expect_equal(slices("777777", 3), c("777", "777", "777", "777"))
+})
+
+test_that("Slices of a long series", {
+  expect_equal(
+    slices("918493904243", 5),
+    c(
+      "91849",
+      "18493",
+      "84939",
+      "49390",
+      "93904",
+      "39042",
+      "90424",
+      "04243"
+    )
+  )
+})
+
+test_that("Slice length is too large", {
+  expect_error(slices("12345", 6))
+})
+
+test_that("Slice length is way too large", {
+  expect_error(slices("12345", 42))
+})
+
+test_that("Slice length cannot be zero", {
+  expect_error(slices("12345", 0))
+})
+
+test_that("Slice length cannot be negative", {
+  expect_error(slices("123", -1))
+})
+
+test_that("Empty series is invalid", {
+  expect_error(slices("", 1))
+})