LeetCode.python.Array.medium.1-5

1. 3. Longest Substring Without Repeating Characters(最长不重复子串)

class Solution:
    def lengthOfLongestSubstring(self, s):
        """
        :type s: str
        :rtype: int
        """
        if len(s) == 0:
            return 0
        
        max_len = 0
        pre_index = {}
        start_index = 0
        for i in range(0, len(s)):
            # 如果当前字符为重复，并且start_index 比当前字符上一次出现的位置靠左或相同，更新start_index 到上一次右侧
            if (s[i] in pre_index.keys()) and (start_index <= pre_index[s[i]]):
                start_index = pre_index[s[i]]+1
            # 没有出现重复，则计算当前最大长度
            else:
                max_len = max(max_len, i-start_index+1)
            pre_index[s[i]] = i

        return max_len