/**

* time: O(N)

* space: O(N)

*/

public class Codec {

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

public String encode(List<String> strs) {

StringBuilder sb = new StringBuilder();

for (String str : strs) {

sb.append(str.length())

.append(':')

.append(str);

}

return sb.toString();

}

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

public List<String> decode(String s) {

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

int i = 0;

while (i < s.length()) {

int searchIndex = s.indexOf(':', i);

int chunkSize = Integer.parseInt(s.substring(i, searchIndex));

i = searchIndex + chunkSize + 1;

decoded.add(s.substring(searchIndex + 1, i));

}

return decoded;

}

}