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RunLengthEncoding.java
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RunLengthEncoding.java
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package com.sushantjhingan;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Scanner;
/**
* Run-length encoding (RLE) is a very simple form of data compression in which runs of data
* (that is, sequences in which the same data value occurs in many consecutive data elements)
* are stored as a single data value and count, rather than as the original run. (Wikipedia)
*
* @author Sushant Jhingan
* Complexity O(n)
*/
public class RunLengthEncoding {
private static String method1(String input) {
StringBuilder output = new StringBuilder();
for (int i = 0, count = 1; i < input.length(); i++) {
if (i + 1 < input.length() && input.charAt(i) == input.charAt(i + 1))
count++;
else {
output = output.append(Integer.toString(count))
.append(Character.toString(input.charAt(i)));
count = 1;
}
}
return output.toString();
}
private static String method2(String source) {
StringBuffer dest = new StringBuffer();
for (int i = 0; i < source.length(); i++) {
int runLength = 1;
while(i+1 < source.length() && source.charAt(i) == (source.charAt(i+1)))
{
runLength++;
i++;
}
dest.append(source.charAt(i));
dest.append(runLength);
}
return dest.toString();
}
private static String method3(String input) {
if(input.equals("") || input.trim().equals("")){
return "";
}
Map<Character, Integer> map = new HashMap<Character, Integer>();
List<Character> list = new ArrayList<Character>();
for(int i=0;i<input.length();i++){
if(map.get(input.charAt(i)) != null){
int count = map.get(input.charAt(i)) + 1;
map.put(input.charAt(i), count);
}else{
map.put(input.charAt(i), 1);
list.add(input.charAt(i));
}
}
StringBuilder builder = new StringBuilder();
for(Character s: list){
builder.append(map.get(s));
builder.append(s);
}
return builder.toString();
}
public static void main(String[] args) {
Scanner scan = new Scanner(System.in);
String s = scan.nextLine();
System.out.println(method1(s));
}
}