[LeetCode] 3. Longest Substring Without Repeating Characters（Python）

1. 题目
2. 题目理解
3. 代码实现

1. 题目

Given a string s, find the length of the longest substring without repeating characters.
Example 1:
Input: s = “abcabcbb”
Output: 3
Explanation: The answer is “abc”, with the length of 3.
Example 2:
Input: s = “bbbbb”
Output: 1
Explanation: The answer is “b”, with the length of 1.
Example 3:
Input: s = “pwwkew”
Output: 3
Explanation: The answer is “wke”, with the length of 3. Notice that the answer must be a substring, “pwke” is a subsequence and not a substring.
Example 4:
Input: s = “”
Output: 0
Constraints:
0 <= s.length <= 5 * 104
s consists of English letters, digits, symbols and spaces.

2. 题目理解

输入一个字符串，输出该字符串中最长不重复子串的字符数。

3. 代码实现

1）思路一
将本位存到字符表中，判断下一位字符是否存在于字符表相同：若不同，temp+1，并加入字符表；若相同，temp_max为当前最长字符数，清空字符表，并从下一位开始判断。但存入字符表再进行字符表的匹配会造成一些冗余。
2）思路二
构建字典dict，起始位start，长度最大值maxl。若字典中存在当位且字典中存储的值+1大于起始位的值，起始位改为当前位+1。将当前位更新到字典中，并将当前最长不重复字符数maxl更新为当前位-start+1与当前maxl中的较大值。

class Solution(object):def lengthOfLongestSubstring(self, s):""":type s: str:rtype: int"""start = 0maxl = 0dict = {}for i, value in enumerate(s):if s[i] in dict and dict[value]+1 > start:start = dict[value] + 1dict[value] = imaxl = max(i-start+1, maxl)return maxl

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[LeetCode] 3. Longest Substring Without Repeating Characters（Python）

[LeetCode] 3. Longest Substring Without Repeating Characters（Python）

1. 题目

2. 题目理解

3. 代码实现

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