[Update exercise] Crypto Square (#539)

* [Update exercise] Crypto Suare

* linter fix

* changed library import

Author: colinleach

exercises/practice/crypto-square/.meta/example.R

@@ -1,37 +1,18 @@
-normalized_plaintext <- function(input) {
-  gsub("[^[:alnum:]]", "", input) |>
-    tolower()
-}
-
-map_plaintext_to_matrix <- function(input) {
-  txt <- normalized_plaintext(input)
-  width <- max(1, nchar(txt) |> sqrt() |> ceiling())
-  ext_len <- ceiling(nchar(txt) / width) * width
-  txt <- sprintf(paste0("%-", ext_len, "s"), txt)
-
-  strsplit(txt, "") |>
-    unlist() |>
-    matrix(ncol = width, byrow = TRUE)
-}
-
-plaintext_segments <- function(input) {
-  if (!nzchar(input)) {
-    return("")
-  }
-  map_plaintext_to_matrix(input) |>
-    apply(MARGIN = 1, paste, collapse = "") |>
-    trimws()
-}
-
-encoded <- function(input) {
-  map_plaintext_to_matrix(input) |>
-    apply(MARGIN = 2, paste, collapse = "") |>
-    trimws() |>
-    paste(collapse = "")
-}
+library(stringr)
 
 ciphertext <- function(input) {
-  map_plaintext_to_matrix(input) |>
-    apply(MARGIN = 2, paste, collapse = "") |>
-    paste(collapse = " ")
+  normalized <- input |> str_to_lower() |> str_remove_all("[^a-z0-9]")
+  if (normalized == "") return("")
+
+  # R matrices are column-major
+  # we will need a transpose to match the problem specification
+  r <- normalized |> nchar() |> sqrt() |> ceiling()
+  c <- (nchar(normalized) / r) |> ceiling()
+  normalized |> 
+    str_pad(c * r, "right") |>
+    str_split_1("") |>
+    matrix(nrow = r, ncol = c) |>
+    t() |>
+    apply(2, str_flatten) |>
+    str_flatten(collapse = " ")
 }

exercises/practice/crypto-square/.meta/template.j2

@@ -0,0 +1,10 @@
+{%- import "generator_macros.j2" as macros with context -%}
+{{ macros.canonical_ref() }}
+
+{{ macros.header() }}
+
+{% for case in cases -%}
+test_that("{{ case["description"] }}", {
+  expect_equal({{ case["property"] }}("{{ case["input"]["plaintext"] }}"), "{{ case["expected"] }}")
+})
+{% endfor %}

exercises/practice/crypto-square/crypto-square.R

@@ -1,15 +1,3 @@
-normalized_plaintext <- function(input) {
-  
-}
-
-plaintext_segments <- function(input) {
-  
-}
-
-encoded <- function(input) {
-
-}
-
 ciphertext <- function(input) {
-
+  
 }

exercises/practice/crypto-square/test_crypto-square.R

@@ -1,68 +1,31 @@
+# These tests are auto-generated with test data from:
+# https://github.com/exercism/problem-specifications/tree/main/exercises/crypto-square/canonical-data.json
+# File last updated on 2026-08-05
+
 source("./crypto-square.R")
 library(testthat)
 
+test_that("empty plaintext results in an empty ciphertext", {
+  expect_equal(ciphertext(""), "")
+})
+test_that("normalization results in empty plaintext", {
+  expect_equal(ciphertext("... --- ..."), "")
+})
 test_that("Lowercase", {
-  expect_equal(normalized_plaintext("Hello"), "hello")
+  expect_equal(ciphertext("A"), "a")
 })
-
 test_that("Remove spaces", {
-  expect_equal(normalized_plaintext("Hi there"), "hithere")
+  expect_equal(ciphertext("  b "), "b")
 })
-
 test_that("Remove punctuation", {
-  expect_equal(normalized_plaintext("@1, 2%, 3 Go!"), "123go")
-})
-
-test_that("empty plaintext results in an empty rectangle", {
-  expect_equal(plaintext_segments(""), "")
-})
-
-test_that("4 character plaintext results in an 2x2 rectangle", {
-  expect_equal(plaintext_segments("Ab Cd"), c("ab", "cd"))
-})
-
-test_that("9 character plaintext results in an 3x3 rectangle", {
-  expect_equal(plaintext_segments("This is fun!"), c("thi", "sis", "fun"))
-})
-
-test_that("54 character plaintext results in an 8x7 rectangle", {
-  expect_equal(
-    plaintext_segments(
-      "If man was meant to stay on the ground, god would have given us roots."
-    ),
-    c(
-      "ifmanwas",
-      "meanttos",
-      "tayonthe",
-      "groundgo",
-      "dwouldha",
-      "vegivenu",
-      "sroots"
-    )
-  )
-})
-
-test_that("empty plaintext results in an empty encode", {
-  expect_equal(encoded(""), "")
-})
-
-test_that("Non-empty plaintext results in the combined plaintext segments", {
-  expect_equal(
-    encoded(
-      "If man was meant to stay on the ground, god would have given us roots."
-    ),
-    "imtgdvsfearwermayoogoanouuiontnnlvtwttddesaohghnsseoau"
-  )
-})
-
-test_that("empty plaintext results in an empty ciphertext", {
-  expect_equal(ciphertext(""), "")
+  expect_equal(ciphertext("@1,%!"), "1")
 })
-
 test_that("9 character plaintext results in 3 chunks of 3 characters", {
   expect_equal(ciphertext("This is fun!"), "tsf hiu isn")
 })
-
+test_that("8 character plaintext results in 3 chunks, the last one with a trailing space", {
+  expect_equal(ciphertext("Chill out."), "clu hlt io ")
+})
 test_that("54 character plaintext results in 8 chunks, the last two with trailing spaces", {
   expect_equal(
     ciphertext(
@@ -71,7 +34,3 @@ test_that("54 character plaintext results in 8 chunks, the last two with trailin
     "imtgdvs fearwer mayoogo anouuio ntnnlvt wttddes aohghn  sseoau "
   )
 })
-
-test_that("normalization results in empty plaintext", {
-  expect_equal(ciphertext("... --- ..."), "")
-})