class Solution(object):

    def lengthOfLongestSubstring(self, s):

        """

        :type s: str

        :rtype: int

        """

        if len(s) <= 0:

            return 0

        res = list()

        maxLen = 0

        for i in s:

            if i in res:

                tmpLen = len(res)

                if tmpLen > maxLen:

                    maxLen = tmpLen

                while True:

                    tmp = res.pop(0)

                    if tmp == i:

                        break

                res.append(i)

            else:

                res.append(i)

        cnt = len(res)

        if cnt > maxLen:

            maxLen = cnt

        return maxLen