Sliding Window Algorithm Explained Clearly | Longest Substring Without Repeating Characters Leetcode

[@GregHogg]

Master Data Structures & Algorithms For FREE at AlgoMap.io!

[@dantemix]

Please never stop this series.

[@gabedailey3249]

Always have trouble visualizing sliding window keep it up dawg

[@mfaani]

This is a great video. It just gives you the main idea needed. And that’s really what we all need for learning about how to code these.

[@sevenscapes]

Great explanation👏👏

[@va3802]

These are helping me with LeetCode while in my freshmen year.🚀

[@vm1662]

These shorts are amazing. Thank you!

[@davea136]

Excellent explanation. Why am I watching this on a Saturday night?

[@masteradvisor594]

Please never stop this

[@_HariHaranR]

Good approach.

[@GregHogg]

Glad you think so!

[@LukeSorvik]

nice explanation

[@Malayalam_learner]

Great video

[@mohitc4289]

dude i used to watch you on ig when you abrey had followrrs wow

[@smash4929]

How simple you want to make it? Greg: YES

[@GregHogg]

Can't believe I missed this... Thank you buddy :)

[@boring-person-rishabh]

In java if they are English alphabets use can use an array with a being 0 index b being 1 index and so on

[@MrEo89]

Great series, just read up on how to do the visualizing and you will have thousands of followers in no time. Quality > quantity, every time. Edit: also, don’t zoom in as much, you’re constantly clipping the sides of the code snippets off. Set a text width of 60 or zoom out to like 50%. Most phones nowadays have great resolution so if anything we can pinch to zoom at our preference.

[@prasad4you57s2]

You made it clear and cool

[@kur0sh1]

if you're using a string you could just use an array of the size if the number of alphabets. Then you could just index the array with something like ['z' - curr_char ]. You still get the access in constant time without the overhead of a hashing function and all you trade for it is a few extra bytes for the array. I really think people should try to do these problems without using built-in data structures and instead should try to implement their own as that helps you so much in getting a better understanding of these algorithms and programming im general.

[@d.g.m.04]

using maps and sets and what not in these is such an overkill for me its crazy, i'd call it lazy programming lmao

[@alwinthomas2288]

Hi should i use cpp over python due to TLE issue??

[@methodsystem4251]

I have a question if I try to solve the same problem using other techniques Leetcode says Error even though my code is correct. Does Leetcode expect us to solve the problem using only one approach?

[@vetiarvind]

what's the difference between sliding window vs 2 pointer?

[@darcash1738]

As I see it there are two variations to the sliding window, based on what I’ve seen so far. Set subset length(in which you move the right pointer until you get to that length, at which point you can increment both left and right to maintain that length) or undetermined subset length like this, which is based on some condition before you set left = right to start a new subset altogether. Is this correct?

[@GregHogg]

Yes you're completely right

[@darcash1738]

@@GregHogg awesome, thanks!

[@anshusarkar7113]

What is the difference between a set and a hash set ?

[@doodledude1976]

So seeing as how s[r] will always be in the set, can i clear the set, add s[r] to it, and say l = r? I’m trying to get rid of the while loop

[@GregHogg]

No, that won't let it slide properly. It needs to expand and contract as needed.

[@lil_jeke]

What’s the TC O(n^2) ?

[@giancarlokuosmanen9723]

O(n)

[@beardbarbe2824]

Great video just dont get why you are using a set here. Since you checking if the element is in the set at each iteration… 🤔

[@prasad4you57s2]

Please add time and space complexity for all the problems

[@GregHogg]

O(n) for both :)

[@KJ-wf1xz]

Why it’s On time complexity when you need to search through a set at least once moving to the right.

[@KJ-wf1xz]

If you have a string with no repeating characters, the length of set grow from 1 to n-1. Does it make this problem On^2 time complexity?

[@rdubb77]

@@KJ-wf1xz array is only traversed once. O(n)

[@HR-pz7ts]

So that's where I was wrong. I was using a hashmap instead. And clearing the map when there was a repeat. I never thought of learning this algorithm as I wanted to come up with it naturally but then again I still have hadhset to learn. So I'm still learning.

[@overbored1337]

Actually a hashmap is better, or even an array. If you make it store an unique incrementing uint32 is you would only need to erase it on every 4 billion run.

[@deleteduser8822]

hmm so is this another expression for two pointers ?

[@GregHogg]

It's definitely an example of using two pointers

[@onlyAI..]

Isn't it O(n2) ??

[@SanSu_Web3]

Why didn't you use a map instead?

[@GregHogg]

You could. No need though nothing to map to

[@riteshkumar-ve3hs]

You are only finding unique characters this way, not the longest unique substring. Your code will return max_len = 4 when input is pwwkew but actual answer is 3.

[@d.g.m.04]

damn you are right. Instead he could have just ran the inner while loop until the character that just occurred on the right is skipped on the left and that guarantees there's only 1 left.

[@healthplanetary]

Wanted in java

[@rohitwaghmode2123]

giving me TLE on gfg 😭 1038/1071

[@ajaymishra1511]

now optimize it

[@misfries6187]

bro this is n^2 u can do better

[@GregHogg]

Actually, it's O(n)! The nested for loop doesn't make it n^2