leetcode 3

给一个字符串，求出最长的没有重复字符出现的字串。

two point直接推就好，右侧指针无法后移时更新一下答案

class Solution(object):    def lengthOfLongestSubstring(self, s):        """        :type s: str        :rtype: int        """        i = 0        vis = []        while (i < 256):        vis.append(0)        i += 1        ns= []        ans = 1        i = 0        j = 0        lenS = len(s)        if (lenS == 0) : return 0        vis[ord(s[0])] = 1                while (i<lenS and j < lenS):            while (j < lenS-1 and vis[ord(s[j+1])] == 0):           j += 1           vis[ord(s[j])] = 1                        ans = max(ans, j - i + 1)                    vis[ord(s[i])] = 0            i += 1        return ans