Created RailFence cipher
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//CipherStreamJava/src/main/java/com/mattrixwv/CipherStreamJava/polySubstitution/RailFence.java
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//Mattrixwv
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// Created: 03-21-22
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//Modified: 03-21-22
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package com.mattrixwv.CipherStreamJava.polySubstitution;
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import java.math.BigDecimal;
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import com.mattrixwv.CipherStreamJava.exceptions.InvalidBaseException;
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import com.mattrixwv.CipherStreamJava.exceptions.InvalidInputException;
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public class RailFence{
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//Variables
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private String inputString;
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private String outputString;
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private StringBuilder[] fence;
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private boolean preserveCapitals;
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private boolean preserveWhitespace;
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private boolean preserveSymbols;
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private void setInputString(String inputString) throws InvalidInputException{
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//Ensure the input string isn't null
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if(inputString == null){
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throw new InvalidInputException("Input cannot be null");
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}
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//Apply removal options
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if(!preserveCapitals){
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inputString = inputString.toUpperCase();
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}
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if(!preserveWhitespace){
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inputString = inputString.replaceAll("\\s", "");
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}
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if(!preserveSymbols){
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inputString = inputString.replaceAll("[^a-zA-Z\\s]", "");
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}
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//Save the string
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this.inputString = inputString;
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//Ensure the string isn't blank
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if(this.inputString.isBlank()){
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throw new InvalidInputException("Input must contain at least 1 letter");
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}
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}
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private void setNumRails(int numRails) throws InvalidBaseException{
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if(numRails <= 0){
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throw new InvalidBaseException();
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}
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fence = new StringBuilder[numRails];
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for(int cnt = 0;cnt < numRails;++cnt){
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fence[cnt] = new StringBuilder();
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}
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}
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private String getCleanInputString(){
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return inputString.replaceAll("[^a-zA-Z]", "");
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}
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private void formatOutput(String outputString){
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StringBuilder output = new StringBuilder();
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int outputLoc = 0;
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for(char ch : inputString.toCharArray()){
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if(Character.isUpperCase(ch)){
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output.append(Character.toUpperCase(outputString.charAt(outputLoc++)));
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}
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else if(Character.isLowerCase(ch)){
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output.append(Character.toLowerCase(outputString.charAt(outputLoc++)));
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}
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else{
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output.append(ch);
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}
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}
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this.outputString = output.toString();
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}
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private String getDecodedStringFromFence(){
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boolean down = true;
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int rail = 0;
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int outsideCol = 0;
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int insideCol = -1;
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StringBuilder output = new StringBuilder();
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while(true){
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if(rail == 0){
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if(outsideCol >= fence[rail].length()){
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break;
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}
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output.append(fence[rail].charAt(outsideCol));
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++insideCol;
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}
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else if(rail == (fence.length - 1)){
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if(outsideCol >= fence[rail].length()){
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break;
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}
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output.append(fence[rail].charAt(outsideCol++));
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++insideCol;
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}
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else{
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if(insideCol >= fence[rail].length()){
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break;
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}
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output.append(fence[rail].charAt(insideCol));
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}
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if(down){
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++rail;
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}
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else{
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--rail;
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}
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if(rail >= fence.length){
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down = false;
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rail -= 2;
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}
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else if(rail < 0){
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down = true;
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rail += 2;
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}
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}
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return output.toString();
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}
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private void encode(){
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boolean up = true;
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int rail = 0;
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for(char ch : getCleanInputString().toCharArray()){
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fence[rail].append(ch);
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//Advance to the next rail
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if(up){
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++rail;
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}
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else{
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--rail;
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}
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//Make sure you're still in bounds
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if(rail == fence.length){
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up = false;
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rail -= 2;
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}
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else if(rail == -1){
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up = true;
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rail += 2;
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}
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}
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StringBuilder output = new StringBuilder();
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for(StringBuilder segment : fence){
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output.append(segment);
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}
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formatOutput(output.toString());
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}
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private void decode(){
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String cleanInputString = getCleanInputString();
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int cycleLength = 2 * (fence.length - 1);
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BigDecimal k = new BigDecimal(cleanInputString.length()).divide(new BigDecimal(cycleLength));
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int numInTopRail = (int)Math.ceil(k.doubleValue());
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int numInMiddleRails = (numInTopRail * 2);
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int numInBottomRail = 0;
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boolean goingDown = true;
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int middleNum = 0;
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if(k.remainder(BigDecimal.ONE).compareTo(new BigDecimal("0.5")) <= 0){
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numInMiddleRails -= 1;
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numInBottomRail = (int)Math.floor(k.doubleValue());
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goingDown = true;
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middleNum = k.remainder(BigDecimal.ONE).multiply(new BigDecimal(cycleLength)).intValue() - 1;
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}
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else{
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numInBottomRail = numInTopRail;
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goingDown = false;
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middleNum = (cycleLength - (k.remainder(BigDecimal.ONE).multiply(new BigDecimal(cycleLength))).intValue());
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}
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fence[0].append(cleanInputString.substring(0, numInTopRail));
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int start = numInTopRail;
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int end = numInTopRail + numInMiddleRails;
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for(int cnt = 1;cnt < (fence.length - 1);++cnt){
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if((!goingDown) && (middleNum >= cnt)){
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end -= 1;
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}
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fence[cnt].append(cleanInputString.substring(start, end));
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start = end;
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end += numInMiddleRails;
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}
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fence[fence.length - 1].append(cleanInputString.substring(start));
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String output = getDecodedStringFromFence();
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formatOutput(output);
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}
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//Constructor
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public RailFence(){
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preserveCapitals = false;
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preserveWhitespace = false;
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preserveSymbols = false;
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}
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public RailFence(boolean preserveCapitals, boolean preserveWhitespace, boolean preserveSymbols){
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this.preserveCapitals = preserveCapitals;
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this.preserveWhitespace = preserveWhitespace;
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this.preserveSymbols = preserveSymbols;
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}
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//Encodes inputString using a Rail Fence of length numRails and returns the result
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public String encode(int numRails, String inputString) throws InvalidBaseException, InvalidInputException{
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//Set the parameters
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setNumRails(numRails);
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setInputString(inputString);
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//Encode
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encode();
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return outputString;
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}
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//Decodes inputString using a Rail Fence of length numRails and returns the result
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public String decode(int numRails, String inputString) throws InvalidBaseException, InvalidInputException{
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//Set the parameters
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setNumRails(numRails);
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setInputString(inputString);
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//Decode
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decode();
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return outputString;
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}
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//Makes sure all variables are empty
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public void reset(){
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inputString = "";
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outputString = "";
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fence = null;
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}
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//Gets
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public String getInputString(){
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return inputString;
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}
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public String getOutputString(){
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return outputString;
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}
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public int getNumRails(){
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return fence.length;
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}
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}
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