【leetcode 刷题】3、无重复字符的最长子串

class Solution:
    def lengthOfLongestSubstring(self, s: str) -> int:
        num = 0
        l = len(s)
        for i in range(l):
            s1 = ""
            s1 = s[i]
            j = 1
            now_num = 1
            while i + j < l:
                if s[i+j] in s1:
                    break
                else:
                    s1 = s1 + s[i+j]
                    j = j + 1
                    now_num = now_num + 1
            if now_num > num:
                num = now_num
        
        return num