无重复字符的最长子串

给定一个字符串，请你找出其中不含有重复字符的 最长子串 的长度。

def lengthOfLongestSubstring(s):
    length = len(s)
    if length < 2:
        return length

    i = 0
    j = 1
    char_set = set(s[0])
    ss_l = 1

    while j < length:
        if s[j] not in char_set:
            char_set.add(s[j])
            j += 1
        else:
            ss_l = max(ss_l, j - i)
            while s[i] != s[j]:
                char_set.remove(s[i])
                i += 1
            i += 1
            j += 1  
    if j == length:
        ss_l = max(ss_l, j - i)
    return ss_l