Answering the Longest Substring Without Repeating Characters in Kotlin I've spend some time working on the problem and got this close fun lengthOfLongestSubstring(s: String): Int { var set = HashSet() var initalChar = 0 var count = 0 s.forEach {r -> while(!set.add(s[r])) set.remove(s[r]) initalChar++ set.add(s[r]) count = maxOf(count, r - initialChar + 1) } return count } I understand that a HashSet is needed to answer the...