Longest substring without repeating characters

Link: https://leetcode.com/problems/longest-substring-without-repeating-characters/

Solution:

Topics: sliding window, set

Intuition
Trivial sliding window problem. The idea here is to shrink the window while the current character exists in the set. After ensuring it’s not in the set, add it to the set and the length of the set is the length of the current substring with only unique characters.

Implementation

def longest_unique_sub(s):
	res = 0
	chars = set()
	l = 0
	for r in range(len(s)):
		while s[r] in chars:
			chars.remove(s[l])
			l += 1
		chars.add(s[r])
		res = max(res, len(chars))
	return res
 
#time: o(n)
#memory: o(n)

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