exercism/elixir/crypto-square/README.md

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2024-08-22 14:12:28 +00:00
# Crypto Square
Welcome to Crypto Square on Exercism's Elixir Track.
If you need help running the tests or submitting your code, check out `HELP.md`.
## 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 "
```
## Source
### Created by
- @jimmbraddock
### Contributed to by
- @amencarini
- @angelikatyborska
- @Cohen-Carlisle
- @devonestes
- @ggpasqualino
- @lpil
- @neenjaw
- @parkerl
- @sotojuan
- @waiting-for-dev
### Based on
J Dalbey's Programming Practice problems - https://users.csc.calpoly.edu/~jdalbey/103/Projects/ProgrammingPractice.html