class Solution {

public String encode(List<String> strs) {

StringBuilder res = new StringBuilder();

for (String s : strs) {

res.append(s.length()).append('|').append(s);

}

return res.toString();

}

/*

* number + | + string

* read number until |

* move pointer, read substring

*

* tc : O(n) when n is the length of encoded string

* sc : O(1)

* */

public List<String> decode(String str) {

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

int start = 0;

while (start < str.length()) {

int cur = start;

//read until |

while (str.charAt(cur) != '|') {

cur++;

}

int length = Integer.parseInt(str.substring(start, cur));

start = cur + 1;

cur = start + length;

res.add(str.substring(start, cur));

start = cur;

}

return res;

}

}