Longest Subarray with sum K | Brute - Better - Optimal | Generate Subarrays 

Let's march ahead, and create an unmatchable DSA course! ❤ Timestamps pleaseeee Use the problem links in the description.

I've been watching this lecture for the last two days, and it was so frustrating that I couldn't understand the concept, even though Raj Bhaiya explained it thoroughly. After putting in about 7-8 hours, I finally understood what was holding me back. Here's what I've learned: 1. map_name.find(value)-> This function returns an iterator to the element with the key `value` if it is present in the map. If the key is not found, it returns an iterator to `map_name.end()`. 2. map_name.end()-> This function returns an iterator one past the last element of the map. If your map has a size of 4 (indexing from 0 to 3), `map_name.end()` will give you an iterator representing index 4, which is beyond the last element. 3. if(map.find(value) != map.end())-> This line was a real pain in my ass so basically this line checks whether the key `value` is present in the map. If `map.find(value)` does not equal `map.end()`, it means the key is found in the map.similarly , if `map.find(value)` equals `map.end()`, the key is not present in the map. Understanding this line was crucial for me. The `.find()` function returns an iterator to the element if it is present, or `map.end()` if it is not. So, the condition `if(map.find(value) != map.end())` essentially means, "if the key `value` is found in the map." If you've read this far, all the best, buddy! I was literally crying inside after watching the video again and again, but if a noob like me can understand it, you will definitely nail it. Haha. Thanks, Raj Bhaiya. ❤

When Striver says no one will teach you in such depth, he means it

To all those whose mind are like " shyd coding is not for me" after seeing this question Take my one advice am the one solving it from 11 :am in the morning and understood it at 7 20 pm of evening I between my mind qas like chod de "pr bhaiya chodna hi toh nhi hai tabhi toh smjega" So give yourself a shootout and say striver bhaiya i will play you once more and play it back to back even if you have watched for 100 times play it slowly took a pen copy and try to understand what bhaiya is saying 🎉🎉

I am following your playlist for DSA. I got subarray of string related problem in my JP Morgan interview. I have explained the approach as you taught. It was quite simple for me to explain the approach as I had watched your this video.. Thank you so much sir you are doing very well.

TIMESTAMPS 0:00 Intro 0:43 Problem Explanation 3:37 Brute force approach 10:50 Better approach (Both positives + negatives) 26:57 Time complexity of Hashing based better solution and why its best for both positives and negatives 28:55 Optimal solution (positives only) 37:52 Time complexity of two pointer based optimal solution

That hashing one went above my mind maybe need to watch it again

Please keep this series continued. Brilliant work Raj. I am speechless. An if anyone reading this, and you have a difficulty understanding, don't give up, just watch 2-3 more times, you shall understand, trust me.

Absolutely brilliant. Haven't seen anyone else on RU-vid explaining any dsa problem with this much clarity.

You are doing a wonderful job man!!! Really grateful to people like you who provide such quality content with such a dedication !!

You are helping families not individuals. Thanks for this.

Teaching is an art and you have nailed it, my friend. Another amazing one from Striver. Thank you!

Those who understand the beauty of ur optimal codes, will agree, ALL UR LEC.S ARE PURE GOLD. U are a gr8 GURU .... sharing such exceptional lec.s for free is superb SERVICE FOR MANKIND. U are empowering youth ... making difficult topics look like easy .... u explain everything so easilty ... study looks like fun when u teach. Codes can revolutionise the world ... can take us to distant planets.... Codes are like miracle ... the way incredible creation like AI is developed .... Sw Er.s are next Gen soldiers of nation. They can fuel engine of growth and contribute in development of nation and growth of humanity. U r doing exceptional work ... Thank for evth..... God bless u ... Tc.

Had to watch it twice to understand it like 95% but did understand it. Really impressive stuff!

Understood! Amazing explanation as always, thank you very very much for your effort!!

Amazing quality, Cant thank you enough. top notch explanation, and nobody teaches DSA in this depth from my learning experience. i dont have words to thank you, may god give you all good health , happiness and wealth to continue this noble cause,

Absolutely Brilliant Explanation !! You explained the problem with so much clarity.

Thank you striver for this ultimate course, I was trying from many days and searching to starts DSA, and this course made me do it Today day 15 😅

Understood !! Both Interviewer And Me Are Super - Duper Impressed !!

This man is a god straight from heaven for programmers. The Clarity he has in his explanation is absolutely Amazing! Never seen a guy who is so passionate teaching DSA. Love you Raj Bhai! ❤

This is the lecture when I understand hashing properly. Thanks striver👍

The best video till now I have seen for this problem . 41 minutes explanation for a single problem is just a next level thing.

Thank you so much for such an easily understandable course.

Outstanding Explaination... I cant able to understand by watching this video even 2 times. It doesnt mean, striver didn't explained well. He explained very well. so, people who are not able to understand it well, try to watch it again and again...! Dont search for other videos for this question, and if you even search, I will assure you that, you cant able to find better explaination than this..! Striver, Thank you so much...!

One of the best explanation for this type problem. Need to see the video 3 times but at the end got it.

That much clarity and explanation 🔥🔥🔥

This lecture is too good 😍🤩 and the Mentor , he obviously needs no introduction 💥

wonderful you've taught both approaches together.

kya aadmi h yaar!! dedication amazing 😍

Watching the video 2nd times, first time was yesterday and now things are getting little inside my head. Thnx Striver.

Amazing!!💗💗 Also, we can further trim down the code provided in 26:46. If we intialize our HashMap with map.put(0,-1), we can skip checking the condition of if(sum==k)

what a crystal clear explaination, understood!

thank you so much striver for everything ,today i did this question on my own without watching video but only with my intution it took me around 3hrs but it felt so good and its all because of you. thanks a lot (raj sir)😇❤ @take U forward !!🔥🔥🔥🔥🔥🔥🔥

Amazing intuition as always!!!!

This is life saving. Salute!

Took me 3-4 passes to finally get the thought process through my head. But UNDERSTOOD it finally :)

You are my inspiration bhaiya .. And I am really a big fan of you, blessing me to become like you.

Making my DSA journey superb ❤ hats off to u

Thank you so much sir 🙏your keep free time to teaching for us

this series is really commendable. Learning a lot.

following and loving this course ❣❣

awesome explanation, i will watch it again and then solve to understand it completely.

excellent explanations as expected.

genuinely one of the best cousrse man!!

Understood in one go. but had to pause a lot and dry run everything in pen paper. nice question!

understood ! Next level explanation sir 🙇‍♂

You are like Virat Kholi.

Understood Bhaiya ❤❤ crystal clear and to be point explanation..!

Awesome sir.Kindly solve String problems as soon as faster. It will be helpful for my placements.

Raj, Thanks a lot for This Amazing Video about C++ Arrays Video - 4 Completed ✅

Understood super explanation as always.

Really power packed video 🥲

That satisfying song at the end .I always wait till the end for that.😂😊❤

One the most Amazing Problem Solving Teaching Technique stepwise thoughtfully!! 🤩Seen ever anywhere!! Great Thanks! Striver😊

In the brute force(only +ve) can i break from the jth loop if the sum > target. Since this is not a subsequence i felt there is no point on adding to the sum if its > target.. Correct me if i am wrong

Heyy Striver, Can we use the variable-sized sliding window approach for this question ??

WE can simplify moving to right is we just initilize the sum to zero: int longestSubarrayWithSumK(vector nums, long long targetSum) { int n = nums.size(); // Size of the array. int left = 0, right = 0; // Two pointers. long long currentSum = 0; // Initialize currentSum to 0. int maxLength = 0; while (right < n) { currentSum += nums[right]; // Add the current element to the currentSum. // If the current sum is greater than the target sum, reduce the subarray from the left // until the current sum becomes less than the target sum. while (left targetSum) { currentSum -= nums[left]; left++; } // If the current sum is equal to the target sum, update the maxLength. if (currentSum == targetSum) { maxLength = max(maxLength, right - left + 1); } // Move the right pointer forward. right++; } return maxLength; }

thank you sir!! for u r wonder lecture and i understood every conceotsir

Thankyou sir for such an elaborate explanation!

a wonderful question and a wonderful explaination.

This is the Bestttttt Videooo I had found on RU-vid

Finally understood the concept 😮‍💨

In the first question, can we break the inner loop if the sum is greater than the required k because the loop only contains positive integers? int longestSubarray(vectorarr, int k){ int maxLength = 0; for(int i = 0; i < arr.size(); i++){ int sum = 0; for(int j = i; j < arr.size(); j++){ sum += arr[j]; if(sum == k){ maxLength = max(maxLength, j-i+1); }else if(sum > k){ break; } } }return maxLength; }

Great work ❤️

can someone explain me the part where we update the map by -- preSumMap[sum] = i;

Can't we do it with if else within one while loop in two pointer methods? And number of subarrays: can't it be done with counter?

Thanks for the video!

Understood much love to you striver

This is called consistency❤❤

nice Lecture. understood clearly bro...

bahut time lag gaya samajhne mai but finally samajh aa hi gaya

understood bhaiya i love this videos and sheet loving the content quality and explanations 🤩😍😇💯

Understood. Thanks for your efforts bro.

Love u striver bhaiya. You are DOPE!

Thank you so much it helped a lot 🙏

Understood great video for arrays problem solving

25:24 I understood what you told but C++ map by defaults takes the right value i.e for input [2 0 0 3] i tried printing (prefixsum,index) hashmap at it printed (5,3) and (2,0) so i guess it never got updated after first insertion.

Understood sir thankyou sir🙏🙇‍♂️❤

18:17 I can't understood the brute solution using hashing. It goes beyond my head😂..

at 28:28 he talks about collisons in case of using unordered_map , what does it mean, can anyone explain me?

You made DSA very interesting😄

Super cool explanation.

best In-depth explanation

understood Great concepts

can someone explain how ordered and unordered maps are effecting the TC.

dil kush kardittaa sir ji ❣

can you add real world applications based on such questions, or approaches.

@Striver JUST FYI. The problem link attached in the striver A to Z sheet is of total count of sub arrays and not longest subarray

Big fan of your teaching and effort anna ❤

It's a bit complex to learn this in the first go. Maybe it would require re-watching the same multiple times.

Watched it 3 times now to toally understand tho it's still a bit unclear but the explanation was really good hope I'll understand if I watch once more

Understood Thank you Striver

But when did we store the sum of the array elements in the map .?? Please anyone help me , how do you store the sum of the elements of array into the map with their indexes?

Would it make a difference in the approach if for the optimal solution we initialize the sum to 0 , rather than initializing it to sum = a[0];

Great explanation

understood. thank you.

brilliant 2 pointer explanation

Amazing explanation striver

That OVERALL was crazy !😂😂

why is my exact same code of 2 pointer approach passing just 3 test cases?? can someone suggest the reason please!