63. leetCode3.Longest Substring Without Repeating Characters【最长不重复子串】

最新推荐文章于 2024-08-14 12:17:19 发布

原创最新推荐文章于 2024-08-14 12:17:19 发布 · 159 阅读

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本文介绍了一种求解字符串中最长无重复字符子串长度的高效算法，并通过Python实现。利用字典记录字符出现的位置，不断更新头指针与最大长度。

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【题目】：

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.

【分析】：youtube讲解使用字典dict来进行计算，pointer指的是头指针

步骤1：检查dict中是否存在当前的字符，若存在则更新pointer位置

步骤2：计算max，为index - pointer + 1

步骤3：更新dict，将已存在的字符的索引更新为当前的索引index

【代码】：

class Solution(object):
    def lengthOfLongestSubstring(self, s):
        """
        :type s: str
        :rtype: int
        """
        tempDict = {}
        pointer = 0
        maxLen = 0
        for key, value in enumerate(s):
            if value in tempDict:
                pointer = max(pointer, tempDict[value]+1)
            maxLen = max(maxLen, key - pointer + 1)
            tempDict[value] = key
        return maxLen