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rail-fence-cipher: update with @FridaTveit's suggestions.
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Lines changed: 96 additions & 18 deletions

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‎config.json‎

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"loops",
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"conditionals"
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],
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"unlocked_by": "atbash-cipher",
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"unlocked_by": "rotational-cipher",
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"uuid": "6e4ad4ed-cc02-4132-973d-b9163ba0ea3d"
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},
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{

‎exercises/rail-fence-cipher/.meta/src/reference/java/RailFenceCipher.java‎

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public class RailFenceCipher {
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import java.util.Arrays;
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private static int key;
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class RailFenceCipher {
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public RailFenceCipher(int key) {
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RailFenceCipher.key = key;
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private int key;
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RailFenceCipher(int key) {
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this.key = key;
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}
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public static String getEncryptedData(String message) {
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String getEncryptedData(String message) {
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String[] lines = splitIntoLines(message, false);
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String result = "";
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StringBuilder result = new StringBuilder();
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for (String line : lines) {
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result += line;
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result.append(line);
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}
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return result;
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return result.toString();
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}
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public static String getDecryptedData(String message) {
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String getDecryptedData(String message) {
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String[] lines = splitIntoLines(message, true);
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int charCount = 0;
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}
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}
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String result = "";
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StringBuilder result = new StringBuilder();
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int lineCount = 0;
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int direction = -1;
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for (int i = 0; i < message.length(); ++i) {
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String letter = String.valueOf(lines[lineCount].charAt(0));
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lines[lineCount] = lines[lineCount].substring(1);
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result += letter;
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result.append(letter);
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direction *= lineCount == 0 || lineCount == key - 1 ? -1 : 1;
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lineCount += direction;
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}
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return result;
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return result.toString();
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}
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private static String[] splitIntoLines(String message, boolean encrypted) {
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private String[] splitIntoLines(String message, boolean encrypted) {
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String[] result = generateEmptyStrings(key);
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int lineCount = 0;
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int direction = -1;
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return result;
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}
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private static String[] generateEmptyStrings(int num) {
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private String[] generateEmptyStrings(int num) {
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String[] strings = new String[num];
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for (int i = 0; i < num; ++i) {
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strings[i] = "";
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}
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Arrays.fill(strings, "");
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return strings;
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}
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‎exercises/rail-fence-cipher/README.md‎

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# Rail Fence Cipher
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Implement encoding and decoding for the rail fence cipher.
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The Rail Fence cipher is a form of transposition cipher that gets its name from
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the way in which it's encoded. It was already used by the ancient Greeks.
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In the Rail Fence cipher, the message is written downwards on successive "rails"
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of an imaginary fence, then moving up when we get to the bottom (like a zig-zag).
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Finally the message is then read off in rows.
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For example, using three "rails" and the message "WE ARE DISCOVERED FLEE AT ONCE",
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the cipherer writes out:
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```text
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W . . . E . . . C . . . R . . . L . . . T . . . E
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. E . R . D . S . O . E . E . F . E . A . O . C .
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. . A . . . I . . . V . . . D . . . E . . . N . .
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```
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Then reads off:
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```text
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WECRLTEERDSOEEFEAOCAIVDEN
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```
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To decrypt a message you take the zig-zag shape and fill the ciphertext along the rows.
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```text
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? . . . ? . . . ? . . . ? . . . ? . . . ? . . . ?
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. ? . ? . ? . ? . ? . ? . ? . ? . ? . ? . ? . ? .
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. . ? . . . ? . . . ? . . . ? . . . ? . . . ? . .
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```
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The first row has seven spots that can be filled with "WECRLTE".
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```text
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W . . . E . . . C . . . R . . . L . . . T . . . E
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. ? . ? . ? . ? . ? . ? . ? . ? . ? . ? . ? . ? .
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. . ? . . . ? . . . ? . . . ? . . . ? . . . ? . .
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```
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Now the 2nd row takes "ERDSOEEFEAOC".
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```text
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W . . . E . . . C . . . R . . . L . . . T . . . E
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. E . R . D . S . O . E . E . F . E . A . O . C .
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. . ? . . . ? . . . ? . . . ? . . . ? . . . ? . .
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```
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Leaving "AIVDEN" for the last row.
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```text
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W . . . E . . . C . . . R . . . L . . . T . . . E
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. E . R . D . S . O . E . E . F . E . A . O . C .
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. . A . . . I . . . V . . . D . . . E . . . N . .
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```
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If you now read along the zig-zag shape you can read the original message.
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To run the tests:
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```sh
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$ gradle test
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```
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For more detailed info about the Java track see the [help page](http://exercism.io/languages/java).
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## Source
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[Wikipedia](https://en.wikipedia.org/wiki/Transposition_cipher#Rail_Fence_cipher)
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## Submitting Incomplete Solutions
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It's possible to submit an incomplete solution so you can see how others have completed the exercise.
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i

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