# fsouza's solution

## to Crypto Square in the D Track

Published at Jul 13 2018 · 0 comments
Instructions
Test suite
Solution

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 downcased.

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

If man was meant to stay on the ground, god would have given us roots.

is normalized to:

ifmanwasmeanttostayonthegroundgodwouldhavegivenusroots

The plaintext should be organized in to a rectangle. The size of the rectangle (`r x c`) should be decided by the length of the message, such that `c >= r` and `c - r <= 1`, where `c` is the number of columns and `r` is the number of rows.

Our normalized text is 54 characters long, dictating a rectangle with `c = 8` and `r = 7`:

``````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:

``````imtgdvsfearwermayoogoanouuiontnnlvtwttddesaohghnsseoau
``````

Output the encoded text in chunks. Phrases that fill perfect rectangles `(r X c)` should be output `c` chunks of `r` length, separated by spaces. Phrases that do not fill perfect rectangles will have `n` empty spaces. Those spaces should be distributed evenly, added to the end of the last `n` chunks.

``````imtgdvs fearwer mayoogo anouuio ntnnlvt wttddes aohghn  sseoau
``````

Notice that were we to stack these, we could visually decode the cyphertext back in to the original message:

``````imtgdvs
fearwer
mayoogo
anouuio
ntnnlvt
wttddes
aohghn
sseoau
``````

## Getting Started

Make sure you have read D page on exercism.io. This covers the basic information on setting up the development environment expected by the exercises.

## Passing the Tests

Get the first test compiling, linking and passing by following the three rules of test-driven development. Create just enough structure by declaring namespaces, functions, classes, etc., to satisfy any compiler errors and get the test to fail. Then write just enough code to get the test to pass. Once you've done that, uncomment the next test by moving the following line past the next test.

``````static if (all_tests_enabled)
``````

This may result in compile errors as new constructs may be invoked that you haven't yet declared or defined. Again, fix the compile errors minimally to get a failing test, then change the code minimally to pass the test, refactor your implementation for readability and expressiveness and then go on to the next test.

Try to use standard D facilities in preference to writing your own low-level algorithms or facilities by hand. DRefLanguage and DReference are references to the D language and D standard library.

## Source

J Dalbey's Programming Practice problems http://users.csc.calpoly.edu/~jdalbey/103/Projects/ProgrammingPractice.html

## Submitting Incomplete Solutions

It's possible to submit an incomplete solution so you can see how others have completed the exercise.

### crypto_square.d

``````module crypto;

unittest
{
immutable int allTestsEnabled = 0;

// normalize_strange_characters
{
auto theCipher = new Cipher("s#\$%^&plunk");
assert("splunk" == theCipher.normalizePlainText());
}

static if (allTestsEnabled)
{
// normalize_numbers
{
auto theCipher = new Cipher("1, 2, 3 GO!");
assert("123go" == theCipher.normalizePlainText());
}

// size_of_small_square
{
auto theCipher = new Cipher("1234");
assert(2U == theCipher.size());
}

// size_of_slightly_larger_square
{
auto theCipher = new Cipher("123456789");
assert(3U == theCipher.size());
}

// size_of_non_perfect_square
{
auto theCipher = new Cipher("123456789abc");
assert(4U == theCipher.size());
}

// size_of_non_perfect_square_less
{
auto theCipher = new Cipher("zomgzombies");
assert(4U == theCipher.size());
}

// plain_text_segments_from_phrase
{
const string[] expected = ["neverv", "exthin", "eheart", "withid", "lewoes"];
auto theCipher = new Cipher("Never vex thine heart with idle woes");
const auto actual = theCipher.plainTextSegments();

assert(expected == actual);
}

// plain_text_segments_from_complex_phrase
{
const string[] expected = ["zomg", "zomb", "ies"];
auto theCipher = new Cipher("ZOMG! ZOMBIES!!!");
const auto actual = theCipher.plainTextSegments();

assert(expected == actual);
}

// Cipher_text_short_phrase
{
auto theCipher = new Cipher("Time is an illusion. Lunchtime doubly so.");
assert("tasneyinicdsmiohooelntuillibsuuml" == theCipher.cipherText());
}

// Cipher_text_long_phrase
{
auto theCipher = new Cipher("We all know interspecies romance is weird.");
assert("wneiaweoreneawssciliprerlneoidktcms" == theCipher.cipherText());
}

// normalized_Cipher_text1
{
auto theCipher = new Cipher("Madness, and then illumination.");
assert("msemo aanin dnin ndla etlt shui" == theCipher.normalize.cipherText());
}

// normalized_Cipher_text2
{
auto theCipher = new Cipher("Vampires are people too!");
assert("vrel aepe mset paoo irpo" == theCipher.normalize.cipherText());
}
}

}``````
``````module crypto;

import std.array: join;
import std.math: round, sqrt;
import std.regex: matchAll, regex;
import std.string;

unittest
{
immutable int allTestsEnabled = 1;

// normalize_strange_characters
{
auto theCipher = new Cipher("s#\$%^&plunk");
assert("splunk" == theCipher.normalizePlainText());
}

static if (allTestsEnabled)
{
// normalize_numbers
{
auto theCipher = new Cipher("1, 2, 3 GO!");
assert("123go" == theCipher.normalizePlainText());
}

// size_of_small_square
{
auto theCipher = new Cipher("1234");
assert(2U == theCipher.size());
}

// size_of_slightly_larger_square
{
auto theCipher = new Cipher("123456789");
assert(3U == theCipher.size());
}

// size_of_non_perfect_square
{
auto theCipher = new Cipher("123456789abc");
assert(4U == theCipher.size());
}

// size_of_non_perfect_square_less
{
auto theCipher = new Cipher("zomgzombies");
assert(4U == theCipher.size());
}

// plain_text_segments_from_phrase
{
const string[] expected = ["neverv", "exthin", "eheart", "withid", "lewoes"];
auto theCipher = new Cipher("Never vex thine heart with idle woes");
const auto actual = theCipher.plainTextSegments();

assert(expected == actual);
}

// plain_text_segments_from_complex_phrase
{
const string[] expected = ["zomg", "zomb", "ies"];
auto theCipher = new Cipher("ZOMG! ZOMBIES!!!");
const auto actual = theCipher.plainTextSegments();

assert(expected == actual);
}

// Cipher_text_short_phrase
{
auto theCipher = new Cipher("Time is an illusion. Lunchtime doubly so.");
assert("tasneyinicdsmiohooelntuillibsuuml" == theCipher.cipherText());
}

// Cipher_text_long_phrase
{
auto theCipher = new Cipher("We all know interspecies romance is weird.");
assert("wneiaweoreneawssciliprerlneoidktcms" == theCipher.cipherText());
}

// normalized_Cipher_text1
{
auto theCipher = new Cipher("Madness, and then illumination.");
assert("msemo aanin dnin ndla etlt shui" == theCipher.normalize.cipherText());
}

// normalized_Cipher_text2
{
auto theCipher = new Cipher("Vampires are people too!");
assert("vrel aepe mset paoo irpo" == theCipher.normalize.cipherText());
}
}

}

void main ()
{
}

class Cipher
{
private string plain;
private ulong r, c;
private bool normalized;

this(string input)
{
plain = norm(input);
setDimensions();
}

private this(string plain, ulong r, ulong c)
{
this.plain = plain;
this.r = r;
this.c = c;
normalized = true;
}

string normalizePlainText()
{
return plain;
}

ulong size()
{
return c;
}

string[] plainTextSegments()
{
string[] segments;
segments.length = r;
int pos = 0;
for (int i = 0; i < r; i++)
{
ulong last = i*c+c;
if (last > plain.length)
last = plain.length;
segments[i] = plain[i*c..last];
}
return segments;
}

string cipherText()
{
auto segments = plainTextSegments();
string[] cipherParts;
cipherParts.length = c;
for (int i = 0; i < c; i++)
{
auto cipher = "";
foreach (string segment; segments)
if (i < segment.length)
cipher ~= segment[i];
cipherParts[i] = cipher;
}
return cipherParts.join(normalized ? " " : "");
}

@property Cipher normalize()
{
return new Cipher(plain, r, c);
}

private void setDimensions()
{
r = cast(ulong)round(sqrt(cast(float)plain.length));
c = r;
if (r * r < plain.length)
c = r + 1;
}

private string norm(string input)
{
auto re = regex("[a-z0-9]+");
auto m = matchAll(input.toLower(), re);
string[] parts;
while (!m.empty)
{
parts ~= m.front.hit;
m.popFront();
}
return parts.join("");
}
}``````