Given a string, find the length of the longest substring without repeating characters.

Examples:

Given "abcabcbb", the answer is "abc", which the length is 3.
Given "bbbbb", the answer is "b", with the length of 1.
Given "pwwkew", the answer is "wke", with the length of 3. Note that the answer must be a substring, "pwke" is a subsequence and not a substring.

翻译：

给定一个字符串，找到最长的、没有重复字符的子字符串，返回其长度。

Solution:

class Solution {
    fun lengthOfLongestSubstring(s: String): Int {
        val arr = BooleanArray(128)
        var head = 0
        var max = 0
        for ((tail, char) in s.withIndex()) {
            val index = char.toInt()
            if (arr[index]) {
                val l = tail - head
                max = if (max > l) max else l
                while (arr[index]) {
                    arr[s[head].toInt()] = false
                    head++
                }
            }
            arr[char.toInt()] = true
        }
        val l = s.length - head
        max = if (max > l) max else l
        return max
    }
}