feat: Add Crypto Square (closes #137) (#138)

config.json

@@ -265,6 +265,14 @@
         "prerequisites": [],
         "difficulty": 1
       },
+      {
+        "slug": "crypto-square",
+        "name": "Crypto Square",
+        "uuid": "39431693-b130-4e1a-a4c1-781eb0226e39",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 4
+      },
       {
         "uuid": "dc522fc7-94e5-4527-ac6e-e713ac4a5ec2",
         "slug": "isogram",

exercises/practice/crypto-square/.docs/instructions.md

@@ -0,0 +1,71 @@
+# Instructions
+
+Implement the classic method for composing secret messages called a square code.
+
+Given an English text, output the encoded version of that text.
+
+First, the input is normalized: the spaces and punctuation are removed from the English text and the message is down-cased.
+
+Then, the normalized characters are broken into rows.
+These rows can be regarded as forming a rectangle when printed with intervening newlines.
+
+For example, the sentence
+
+```text
+"If man was meant to stay on the ground, god would have given us roots."
+```
+
+is normalized to:
+
+```text
+"ifmanwasmeanttostayonthegroundgodwouldhavegivenusroots"
+```
+
+The plaintext should be organized into a rectangle as square as possible.
+The size of the rectangle should be decided by the length of the message.
+
+If `c` is the number of columns and `r` is the number of rows, then for the rectangle `r` x `c` find the smallest possible integer `c` such that:
+
+- `r * c >= length of message`,
+- and `c >= r`,
+- and `c - r <= 1`.
+
+Our normalized text is 54 characters long, dictating a rectangle with `c = 8` and `r = 7`:
+
+```text
+"ifmanwas"
+"meanttos"
+"tayonthe"
+"groundgo"
+"dwouldha"
+"vegivenu"
+"sroots  "
+```
+
+The coded message is obtained by reading down the columns going left to right.
+
+The message above is coded as:
+
+```text
+"imtgdvsfearwermayoogoanouuiontnnlvtwttddesaohghnsseoau"
+```
+
+Output the encoded text in chunks that fill perfect rectangles `(r X c)`, with `c` chunks of `r` length, separated by spaces.
+For phrases that are `n` characters short of the perfect rectangle, pad each of the last `n` chunks with a single trailing space.
+
+```text
+"imtgdvs fearwer mayoogo anouuio ntnnlvt wttddes aohghn  sseoau "
+```
+
+Notice that were we to stack these, we could visually decode the ciphertext back in to the original message:
+
+```text
+"imtgdvs"
+"fearwer"
+"mayoogo"
+"anouuio"
+"ntnnlvt"
+"wttddes"
+"aohghn "
+"sseoau "
+```

exercises/practice/crypto-square/.meta/config.json

@@ -0,0 +1,19 @@
+{
+  "authors": [
+    "keiravillekode"
+  ],
+  "files": {
+    "solution": [
+      "crypto-square.v"
+    ],
+    "test": [
+      "run_test.v"
+    ],
+    "example": [
+      ".meta/example.v"
+    ]
+  },
+  "blurb": "Implement the classic method for composing secret messages called a square code.",
+  "source": "J Dalbey's Programming Practice problems",
+  "source_url": "https://users.csc.calpoly.edu/~jdalbey/103/Projects/ProgrammingPractice.html"
+}

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

@@ -0,0 +1,47 @@
+module main
+
+fn columns(n int) int {
+	mut c := 0
+	for c * c < n {
+		c += 1
+	}
+	return c
+}
+
+fn rows(n int, c int) int {
+	mut r := c - 1
+	if r * c < n {
+		r += 1
+	}
+	assert r * c >= n
+	return r
+}
+
+fn ciphertext(plaintext string) string {
+	mut normalized := []u8{cap: plaintext.len}
+	for ch in plaintext.to_lower() {
+		if ch.is_alnum() {
+			normalized << ch
+		}
+	}
+
+	n := normalized.len
+	if n <= 1 {
+		return normalized.bytestr()
+	}
+	c := columns(n)
+	r := rows(n, c)
+
+	mut buffer := []u8{len: (r + 1) * c - 1, init: u8(` `)}
+	mut index := 0
+	for i in 0 .. r {
+		for j in 0 .. c {
+			buffer[j * (r + 1) + i] = normalized[index]
+			index += 1
+			if index == n {
+				break
+			}
+		}
+	}
+	return buffer.bytestr()
+}

exercises/practice/crypto-square/.meta/tests.toml

@@ -0,0 +1,27 @@
+# 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.
+
+[407c3837-9aa7-4111-ab63-ec54b58e8e9f]
+description = "empty plaintext results in an empty ciphertext"
+
+[aad04a25-b8bb-4304-888b-581bea8e0040]
+description = "normalization results in empty plaintext"
+
+[64131d65-6fd9-4f58-bdd8-4a2370fb481d]
+description = "Lowercase"
+
+[63a4b0ed-1e3c-41ea-a999-f6f26ba447d6]
+description = "Remove spaces"
+
+[1b5348a1-7893-44c1-8197-42d48d18756c]
+description = "Remove punctuation"
+
+[8574a1d3-4a08-4cec-a7c7-de93a164f41a]
+description = "9 character plaintext results in 3 chunks of 3 characters"
+
+[a65d3fa1-9e09-43f9-bcec-7a672aec3eae]
+description = "8 character plaintext results in 3 chunks, the last one with a trailing space"
+
+[fbcb0c6d-4c39-4a31-83f6-c473baa6af80]
+description = "54 character plaintext results in 7 chunks, the last two with trailing spaces"

exercises/practice/crypto-square/crypto-square.v

@@ -0,0 +1,4 @@
+module main
+
+fn ciphertext(plaintext string) string {
+}

exercises/practice/crypto-square/run_test.v

@@ -0,0 +1,49 @@
+module main
+
+fn test_empty_plaintext_results_in_an_empty_ciphertext() {
+	phrase := ''
+	expect := ''
+	assert ciphertext(phrase) == expect
+}
+
+fn test_normalization_results_in_empty_plaintext() {
+	phrase := '... --- ...'
+	expect := ''
+	assert ciphertext(phrase) == expect
+}
+
+fn test_lowercase() {
+	phrase := 'A'
+	expect := 'a'
+	assert ciphertext(phrase) == expect
+}
+
+fn test_remove_spaces() {
+	phrase := '  b '
+	expect := 'b'
+	assert ciphertext(phrase) == expect
+}
+
+fn test_remove_punctuation() {
+	phrase := '@1,%!'
+	expect := '1'
+	assert ciphertext(phrase) == expect
+}
+
+fn test_9_character_plaintext_results_in_3_chunks_of_3_characters() {
+	phrase := 'This is fun!'
+	expect := 'tsf hiu isn'
+	assert ciphertext(phrase) == expect
+}
+
+fn test_8_character_plaintext_results_in_3_chunks_the_last_one_with_a_trailing_space() {
+	phrase := 'Chill out.'
+	expect := 'clu hlt io '
+	assert ciphertext(phrase) == expect
+}
+
+fn test_54_character_plaintext_results_in_7_chunks_the_last_two_with_trailing_spaces() {
+	phrase := 'If man was meant to stay on the ground, god would have given us roots.'
+	expect := 'imtgdvs fearwer mayoogo anouuio ntnnlvt wttddes aohghn  sseoau '
+	assert ciphertext(phrase) == expect
+}