003.最长无重复子字符串.py

class Solution(object):
    def lengthOfLongestSubstring(self, s):
        """
        :type s: str
        :rtype: int
        """
        # 哈希表+单指针：O(n)
        used = {}
        max_length, start = 0, 0
        for i, c in enumerate(s):
            if c in used and start <= used[c]:
                start = used[c] + 1
            else:
                max_length = max(max_length, i - start + 1)
            used[c] = i

        return max_length