Run Length Encoding (RLE) is an algorithm for compressing strings, which is specifically useful in compressing binary values. aabccaabaad <--> 2a1b2c2a1b2a1d Implement RLE algorithm for compression and decompression of strings.

LRE.java

public class RunLengthEncoding {
	
	public static String LRE(String str){
		
		StringBuilder test = new StringBuilder();
		int count = 1;
		char[] chars = str.toCharArray();
		 for(int i=0;i<chars.length;i++){
			 char c = chars[i];
			 while( i+1<chars.length && c == chars[i+1]){
				 count++;
				 i++;
				 
			 }
			 
			 test.append(count).append(c);
			 count = 1;
		 }
			 
		 return test.toString();
		
	}
	
	public static String deCompression(String str){
		
		StringBuilder test =new StringBuilder();
		char[] chars = str.toCharArray();
		int n = chars.length;
		
		for(int i = 0;i<n;i=i+2){
			
			char d =chars[i];
			int a = Character.getNumericValue(d);
			char b = chars[i+1];
			
			for(int j=0;j<a;j++){
				test.append(b);
			}
			
		}
		return test.toString();
		
	}
	
	public static void main(String[]args){
		
		String test = "aabccaabaad";
		System.out.println(LRE(test));
		System.out.println(deCompression("2a1b2c2a1b2a1d"));
		
	}

}