fun lengthOfLongestSubstring(s: String): Int {
        fun isUnique(s: String): Boolean = s.toCharArray().distinct() == s.toCharArray().toList() 
        var j = 0; var longest = 0
        for ((i, c) in s.withIndex()) {
            while (isUnique(s.substring(i, j))) {
                if ((j - i) > longest) longest = j - i
                if (j <= s.length - 1) j += 1 else break
            }
            if (longest > s.length-i) break
        }
        return longest
    }