[LeetCode]Longest Substring Without Repeating Characters@python

最新推荐文章于 2025-09-06 17:22:57 发布

原创最新推荐文章于 2025-09-06 17:22:57 发布 · 101 阅读

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#leetcode

本文介绍了一种求解字符串中最长无重复字符子串的高效算法。通过使用哈希表来跟踪字符出现的位置，该算法能在一次遍历内找到最长的无重复字符子串及其长度。

Given a string, find the length of the longest substring without repeating characters.

Examples:

Given "abcabcbb", the answer is "abc", which the length is 3.

Given "bbbbb", the answer is "b", with the length of 1.

Given "pwwkew", the answer is "wke", with the length of 3. Note that the answer must be a substring, "pwke" is a subsequence and not a substring.

求连续不重复最大子串长度。

思路：这里要管理一个dict（Hash），初始化一个start=0,当dict中存在当前字母时，更新字母的value，并更新start。

这里有个小坑：如abba这种，因为后一个a跟前一个a差3个长度，但中间已经有重复，所以要加限制条件start<=usedChar[s[i]]

class Solution(object):
    def lengthOfLongestSubstring(self, s):
        """
        :type s: str
        :rtype: int
        """
        dict = {}
        length = start = 0
        for i in range(len(s)):
            if s[i] in dict and start <= dict[s[i]]:
                start = dict[s[i]]+1
            else:
                length = max(length, i-start+1)
            dict[s[i]] = i
        return length