How does python find the longest substring without repeating characters

This article mainly introduces the relevant knowledge of "how to find the longest substring of non-repetitive characters in python". The editor shows you the operation process through an actual case. The method of operation is simple and fast, and it is practical. I hope this article "how to find the longest substring of non-repetitive characters in python" can help you solve the problem.

[title]

Given a string, please find out the length of the longest substring that does not contain repeating characters.

Example 1:

Enter: "abcabcbb"

Output: 3

Explanation: because the longest substring of non-repeating characters is "abc", its length is 3.

Example 2:

Enter: "bbbbb"

Output: 1

Explanation: because the longest substring of non-repeating characters is "b", its length is 1.

Example 3:

Enter: "pwwkew"

Output: 3

Explanation: because the longest substring of non-repeating characters is "wke", its length is 3.

Please note that your answer must be the length of the substring. "pwke" is a subsequence, not a substring.

[ideas]

1. Brute force cracking: a two-layer for loop traverses all substrings to determine whether there are repetitive elements and record the longest substring length.

2. Hash table: traverses the array, using hash to store elements and their subscripts. When traversing, when the element nums [I] exists in the hash table, the subscript needs to be updated, as well as the longest substring length.

[code]

Python version

Class Solution:

Def lengthOfLongestSubstring (self, s: str)-> int:

D = {}

Last_index = 0

Res = 0

For I, si in enumerate (s):

# in dict, the substring length may be longer

# last_index updated to d [si] + 1

If si ind and d [si] > = last_index:

Res = max (res, I-last_index)

Last_index = d [si] + 1

# Update the si of dict

D [si] = I

# Note, it has not been compared with the last paragraph

Res = max (res, len (s)-last_index)

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