import java.util.ArrayList;

import java.util.Arrays;

import java.util.List;

import java.util.stream.Collectors;

public class Solution {

/*

* @param strs: a list of strings

* @return: encodes a list of strings to a single string.

*/

String cDel = "&";

String sDel = ";";

// Encodes a list of strings to a single string

public String encode(List<String> strs) {

if (strs.isEmpty()) return null;

StringBuilder result = new StringBuilder();

for (int i =0; i<strs.size(); i++) {

String str = strs.get(i);

StringBuilder temp = new StringBuilder();

for (char c : str.toCharArray()) {

temp.append((int) c).append(cDel);

}

result.append(temp);

if (i != strs.size()-1) result.append(sDel);

}

return result.toString();

}

// Decodes a single string to a list of strings

public List<String> decode(String str) {

if (str==null)

return new ArrayList<>();

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

String[] strs = str.split(sDel, -1);

for (String s : strs) {

if (s.isEmpty()) {

result.add("");

continue;

}

String[] chars = s.split(cDel);

String decoded = Arrays.stream(chars)

.filter(sr -> !sr.isEmpty())

.mapToInt(Integer::parseInt)

.mapToObj(ascii -> (char) ascii)

.map(String::valueOf)

.collect(Collectors.joining());

result.add(decoded);

}

return result;

}

}