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:
The plaintext should be organized in to a rectangle. The size of the
r x c) should be decided by the length of the message,
c >= r and
c - r <= 1, where
c is the number of columns
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:
Output the encoded text in chunks that fill perfect rectangles
(r X c),
c chunks of
r length, separated by spaces. For phrases that are
n characters short of the perfect rectangle, pad each of the last
chunks with a single trailing space.
"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 "
J Dalbey's Programming Practice problems http://users.csc.calpoly.edu/~jdalbey/103/Projects/ProgrammingPractice.html
It's possible to submit an incomplete solution so you can see how others have completed the exercise.
(ns crypto-square-test (:require [clojure.test :refer [deftest is]] crypto-square)) (deftest normalize-splunk (is (= "splunk" (crypto-square/normalize-plaintext "s#!@$%plunk")))) (deftest normalize-with-punctuation (is (= "123go" (crypto-square/normalize-plaintext "1, 2, 3 GO!")))) (deftest square-2 (is (= 2 (crypto-square/square-size "1234")))) (deftest square-3 (is (= 3 (crypto-square/square-size "123456789")))) (deftest square-4 (is (= 4 (crypto-square/square-size "123456789abc")))) (deftest segments (is (= ["neverv", "exthin", "eheart", "withid", "lewoes"] (crypto-square/plaintext-segments "Never vex thine heart with idle woes.")))) (deftest segments-2 (is (= ["zomg", "zomb", "ies"] (crypto-square/plaintext-segments "ZOMG! ZOMBIES!!!")))) (deftest cipher-1 (is (= "tasneyinicdsmiohooelntuillibsuuml" (crypto-square/ciphertext "Time is an illusion. Lunchtime doubly so.")))) (deftest cipher-2 (is (= "wneiaweoreneawssciliprerlneoidktcms" (crypto-square/ciphertext "We all know interspecies romance is weird.")))) (deftest cipher-3 (is (= "msemo aanin dnin ndla etlt shui" (crypto-square/normalize-ciphertext "Madness, and then illumination.")))) (deftest cipher-4 (is (= "vrel aepe mset paoo irpo" (crypto-square/normalize-ciphertext "Vampires are people too!")))) (deftest cipher-5 (is (= (str "ageihdsednsh lsagtoonaepe lannswnccair hrditeaetnrh " "ueethdnatoio mbqyewdnotto aouayicdwhod nranatosaef " "bnldrhnhrrb efirersodir irnieecusno nedgnailoat") (let [plaintext (str "All human beings are born free " "and equal in dignity and rights. " "They are endowed with reason and conscience " "and should act towards one another " "in a spirit of brotherhood.")] (crypto-square/normalize-ciphertext plaintext)))))
(require '[clojure.string :as str]) (declare make-words padded-segments columns) (defn normalize-plaintext [s] (-> s (str/replace #"\W" "") str/lower-case)) (defn square-size [s] (int (Math/ceil (Math/sqrt (count s))))) (defn plaintext-segments [s] (->> s padded-segments make-words)) (defn ciphertext [s] (->> s columns make-words (apply str))) (defn normalize-ciphertext [s] (->> s ciphertext (partition-all 5) make-words (str/join \space))) (defn- make-words [s] ;; Make strings from nested character sequences. (map (partial apply str) s)) (defn- padded-segments [s] ;; Transform into square rows, last row is nil-padded. (let [normalized (normalize-plaintext s) size (square-size normalized)] (partition size size (repeat nil) normalized))) (defn- columns [s] ;; Transform rows into colums. (->> s padded-segments (apply map vector)))
A huge amount can be learned from reading other people’s code. This is why we wanted to give exercism users the option of making their solutions public.
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