import java.util.ArrayList;

import java.util.List;

public class Codec {

String SPLIT = ":";

// Encodes a list of strings to a single string.

public String encode(List<String> strs) {

StringBuilder encoded = new StringBuilder();

for(String str : strs) {

encoded.append(str.length()).append(SPLIT).append(str);

}

return encoded.toString();

}

// Decodes a single string to a list of strings.

public List<String> decode(String s) {

List<String> decoded = new ArrayList<>();

int pointer = 0;

while(pointer < s.length()) {

int index = s.indexOf(SPLIT, pointer);

int length = Integer.parseInt(s.substring(pointer, index));

String str = s.substring(index + 1, index + 1 + length);

decoded.add(str);

pointer = index + 1 + length;

}

return decoded;

}

}

// Your Codec object will be instantiated and called as such:

// Codec codec = new Codec();

// codec.decode(codec.encode(strs));