Decoder Works - Pull Request - Rhea

README.txt

@@ -10,3 +10,6 @@ do the decoding algorithm.
 
 There's also a bunch of explanation about BitWriter, a writer class I made to write bits out, so you can
 look at the comments for that if you want.
+
+
+UPDATE: Decoder works in conjunction with Encoder for all three test files. Modeled after GeekforGeeks algorithm. - Rhea 

decoded.txt

@@ -1 +1 @@
-0000011000010000011000100000011000110001000000000001000000100001000000010001000000110001000001100001000001010001000010000001000001000001000010100001000001110001000010110001000010010001000011000001000011110001000011100001000100010001000011010001000100110001000100000001000101000001000100100001000101010001000110000001000101110001000110100001000101100001000111000001000110010001000111010001000110110001000111100001001000010001001000000001000110110000011001000000011001010000011001100000011001110001001000100001000111110001001010100001001010010001001011000001001000110000011000110001001001010001001001110001001011010001001010110001001011100001001100100001001101010001001101000001001101110001001100110001001110010001001101100001001110100001001110000001001110110001001111100001001111010001010000000001001111000001010000100001001111110001010000110001010000010001010001000001010001110001010001100001010010010001010001010001010010110001010010000000011000110000
+abcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcdefgabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcdefgabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabc

original.txt

@@ -1 +1 @@
-abcabcabcabcabcabcabcabcabcabcabcabc
+abcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcdefgabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcdefgabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabc

src/Decoder.java

@@ -2,20 +2,72 @@
 import java.io.*;
 public class Decoder {
 
+
 
 	//public static final int BITS = 12;
 	public static void main(String[] args) throws IOException{
 		// TODO Auto-generated method stub
 		FileInputStream in = new FileInputStream("encoded.txt");//reader
 		PrintWriter out = new PrintWriter(new BufferedWriter(new FileWriter("decoded.txt")));
+		HashMap<Integer,String> decodeMap = new HashMap<Integer,String>();
+		int counter = 0;
 
-		StringBuilder ans = new StringBuilder();
+		for (int i=0; i<256; i++) //initializing existing ascii values in hashmap
+		{
+			decodeMap.put(counter,String.valueOf((char)(i)));
+			counter++;
+		}
+
+		//bits to binary
+		StringBuilder binary = new StringBuilder();
 		byte[] bits = in.readAllBytes();
 		for(int i =0;i<bits.length;i++)
 		{
 			System.out.println(bits[i]+" "+toBinary(bits[i]));
-			out.print(toBinary(bits[i]));
+			//out.print(toBinary(bits[i]));
+			binary.append(toBinary(bits[i]));
+		}
+
+		//start rebuilding dictionary
+		int currentInt, nextInt;//currentInt = old, nextInt = new
+		String s,c, nextBin, currentBin;
+		c = "";
+
+		for(int i = 0; i<= binary.length()-12; i+=12) 
+		{
+
+			currentBin = binary.substring(i,i+12);
+			currentInt = binaryToInt(currentBin);
+			if(i+24 <= binary.length()-1) {
+				 nextBin = binary.substring(i+12, i+24);
+			}
+			else {
+				nextBin = binary.substring(i+12, binary.length());
+			}
+				nextInt = binaryToInt(nextBin); 	
+
+
+			if (!decodeMap.containsKey(nextInt)) { // if the key's value doesnt exist
+				s  = decodeMap.get(currentInt); //string/character of current binary 
+				s += c ; // current + first of next (defined below - will defintiley run the else statement first
+				//decodeMap.put(counter++,  "" + s );//add it bc it doesnt exist yet
+			}
+			else {
+				s = decodeMap.get(nextInt); //next binary combo's letter/character/string 
+
+				//dont have to set old = newInt because reading in binary 12 at a time with for loop
+			}
+			c = s.substring(0,1);  //first character of s
+			decodeMap.put(counter++,  "" + decodeMap.get(currentInt) + c );
+			out.print(decodeMap.get(currentInt));
 		}
+
+		//need to have a maximum size?
+
+	//	https://www.geeksforgeeks.org/lzw-lempel-ziv-welch-compression-technique/
+
+
+
 		/*
 		while(true)
 		{
@@ -41,6 +93,7 @@ public static void main(String[] args) throws IOException{
 			out.println(ans.substring(i,i+12));
 			i = i+12;
 		}*/
+
 		out.close();
 
 	}
@@ -59,5 +112,14 @@ public static String toBinary(int a)
 		ans.append(cur);
 		return ans.toString();
 	}
+
+	public static int binaryToInt(String binary){
+
+		return Integer.parseInt(binary,2);
+
+	}
+
+
 
+
 }