99 lines
2.3 KiB
Markdown
99 lines
2.3 KiB
Markdown
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# Crypto Square
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Welcome to Crypto Square on Exercism's Elixir Track.
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If you need help running the tests or submitting your code, check out `HELP.md`.
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## Instructions
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Implement the classic method for composing secret messages called a square code.
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Given an English text, output the encoded version of that text.
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First, the input is normalized: the spaces and punctuation are removed from the English text and the message is down-cased.
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Then, the normalized characters are broken into rows.
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These rows can be regarded as forming a rectangle when printed with intervening newlines.
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For example, the sentence
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```text
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"If man was meant to stay on the ground, god would have given us roots."
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```
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is normalized to:
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```text
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"ifmanwasmeanttostayonthegroundgodwouldhavegivenusroots"
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```
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The plaintext should be organized into a rectangle as square as possible.
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The size of the rectangle should be decided by the length of the message.
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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:
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- `r * c >= length of message`,
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- and `c >= r`,
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- and `c - r <= 1`.
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Our normalized text is 54 characters long, dictating a rectangle with `c = 8` and `r = 7`:
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```text
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"ifmanwas"
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"meanttos"
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"tayonthe"
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"groundgo"
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"dwouldha"
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"vegivenu"
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"sroots "
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```
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The coded message is obtained by reading down the columns going left to right.
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The message above is coded as:
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```text
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"imtgdvsfearwermayoogoanouuiontnnlvtwttddesaohghnsseoau"
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```
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Output the encoded text in chunks that fill perfect rectangles `(r X c)`, with `c` chunks of `r` length, separated by spaces.
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For phrases that are `n` characters short of the perfect rectangle, pad each of the last `n` chunks with a single trailing space.
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```text
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"imtgdvs fearwer mayoogo anouuio ntnnlvt wttddes aohghn sseoau "
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```
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Notice that were we to stack these, we could visually decode the ciphertext back in to the original message:
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```text
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"imtgdvs"
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"fearwer"
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"mayoogo"
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"anouuio"
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"ntnnlvt"
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"wttddes"
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"aohghn "
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"sseoau "
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```
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## Source
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### Created by
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- @jimmbraddock
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### Contributed to by
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- @amencarini
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- @angelikatyborska
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- @Cohen-Carlisle
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- @devonestes
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- @ggpasqualino
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- @lpil
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- @neenjaw
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- @parkerl
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- @sotojuan
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- @waiting-for-dev
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### Based on
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J Dalbey's Programming Practice problems - https://users.csc.calpoly.edu/~jdalbey/103/Projects/ProgrammingPractice.html
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