When I first started DSA, I was just so scared of the code and knowing very little about the logic and the intuition behind but Striver you are the one who has ever showed the completely difference - Extreme natural approach and observation and crystal clear logic. You've made the coding fun and interesting toward people like me. Hats off for your dedication! Understood!

@utkarshverma3314

10 ай бұрын

i am doing his dsa sheet , the array part and almost every question has a completely different logic and approach and its becoming quite frustrating as im not able to come up with the solutions so do i just keep solving more problems or am i doing something wrong

@anshlyk

10 ай бұрын

keep going! I was in the same boat, you'll slowly be able to form logic@@utkarshverma3314

@akworld2739

9 ай бұрын

@@utkarshverma3314 same problem i am also facing

@VivekKumar-kx2zf

3 ай бұрын

ashishbhattacharyya yup, it works for me.

@Sankalp-sd6fm

3 ай бұрын

could you please tell if i should make notes ?? how do i make them so that i dont put hours in it

I saw this video at around 10 am in college, was only able to think of o(n²) solution, I took the pause at your hint of using prefix sum array, kept thinking for some time while in college lectures but was able to get the solution at around 6pm 😝, I know it took time but it felt good to actually think of the solution, please keep up the consistency

This man is my hero, I struggled so much with this question to visualize it and subsequent problems like it. I've done ove 270 LC questions, but this man made it so simple

Just when I think the video is getting long enough for a simple problem, I go search the web and find not a single tutor with such a powerful explanation!

understood bhaiya . You can not even imagine how much people love u and praise you and speak about your videos all the time. I am sure u get hiccups every now and then . Live long bhaiya u are our real teacher.

Its really amazing that you are taking your time in explaining via the dry run. It helps me a lot. Thanks :)

I saw many times but I couldn't understand...But now i finally understood and realised that ur explaination is too good...!

Thank you so much. I saw many other youtuber's video but this video is the best . I was able to understand after watching this video for 2 times

This explanation is so 100x better than Neetcode's. Thank you !!!

16:29 if we write if(sum==k) count++ We don't need to include 0 at beginning

@user-tm1hu4cw3v

Ай бұрын

good one!!

@abhijitkumarsinha

Ай бұрын

THAT IS WHAT I WAS DOING

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

Struggled to understand this solution, now understood, Keep up the great work Striver

Amazingly Understood, Thank you for such a in depth thought process

You have given more than anyone can ask for. Thank you for all your support and such amazing videos. They are really helpful. Just a small thing can we have a dark mode setting for "take you forward" pages.

@takeUforward

Жыл бұрын

You can build one chrome extension may be ;)

@dom47

Жыл бұрын

appreciates striver by telling "u have given more than anyone can ask" and proceeds to place demand .

@yashjoon3889

Жыл бұрын

@@takeUforward lol would be a good project for the resume?

@manvinmusic9239

Жыл бұрын

striver actually give the dark mode option

That's really amazing 🤩Striver! code is too sort but logic is superb for the optimal. from brute (TC-> O(N^2), SC -> O(1)) to optimal (TC -> O(N) when using unordered_map, O(N * log N) when using ordered map, SC -> O(N) for using map data structure.

Instead of adding 0 in the hashmap, we can just use the statement if(sum==k) ans++; That works fine. See the Below Code int subarraySum(vector& nums, int k) { int ans=0; unordered_map x; int sum=0; for(int i=0;i

@00RohitRoshan

11 ай бұрын

very good .

@00RohitRoshan

11 ай бұрын

` if(x.find(sum-k)!=x.end()) ans+=x[sum-k]; ` And why this check before incrementing and. class Solution { public: int subarraySum(vector& nums, int k) { int ans=0,sum=0; unordered_map x; for(int i=0;i

@kushalswarup2662

10 ай бұрын

brilliant

Excellent explanation yaar! Great to see such kind of explanations that guide from brute force to optimised solution in such a detail! Thank you so much and keep making such great videos :)

thanks striver you have really explained this so well god bless you you are a wonderful teacher for many 🙏🙏

Understood Bhaiya! This was a tough one to understand for me...will soon revisit it Thank you🙏

So here, if in the question it is stated that it contains only positive as in codestudio then we can apply 2-pointer(Sliding window) as done in longest subarray with sum k. TC: O(N) SC: O(1) Else, if it contains both positive and negative HashMap is optimal

Excellent explanation, understood ! ✨

Previous explanation and current explanation is good .understood

Really good explanation & kudos to efforts, understood 👍

Understood Striver ❤. You are a living legend sir. 🤩🤩

God for beginner❤hats of u bhaiya

Was able to think O(N^2) approach and totally underatood optimal solution too 😊

Understood. Thank you so much!

Striver you are great 🙌🙌 .I just want to thank you ❤️.

Timestamps 01:03 - Problem Statement 01:13 - Sub-array definition 01:52 - Example 03:13 - Brute force solution 06:07 - Complexity 06:29 - Better solution 08:07 - Complexity 08:21 - Optimal Solution 08:41 - Prefix sum concept 09:35 - Example 13:55 - Dry run 21:22 - Code 22:38 - Complexity

Thanks for the great video. I don't see how I can come up with the optimal solution during the interview without hint from the interviewer.

Hi bhaiya it would be really helpful if you can give similar question links for practise after every question explanation!!

Understood💖amazing explanation

for me optimal is little hard but after see 2-3 time video , got easly understand

Sir, May I know time complexity of the optimal approach in java

understood sir ,great explanation

tks for explanation, you are savior

The sliding window approach actually performs better with O(n) time complexity. int subarraySum(vector& nums, int sum) { int count = 0; int currSum = 0; unordered_map sumFreq; for (int i = 0; i currSum += nums[i]; if (currSum == sum) count++; if (sumFreq.find(currSum - sum) != sumFreq.end()) count += sumFreq[currSum - sum]; sumFreq[currSum]++; // If currSum becomes greater than sum, // subtract elements from the start while (currSum > sum) { currSum -= nums[i - count + 1]; sumFreq[currSum]--; if (sumFreq[currSum] == 0) sumFreq.erase(currSum); count--; } } return count; }

22:54 *please explain what lines* int remove = presum - k; count += mp[remove]; mp[presum]++; do ?

understood captain...thanks

Can we do this first calculate the prefix sum and than suffix sum and than we subtract each and sum the prefix and suffix

if instead of specifying map[0]=1 in the beginning if we give a condition that if(preSum == k) { count ++;} Will it be correct Striver bhaiya??

understood ,thnx for amazing video ❤❤❤❤❤❤

Understood, thank you.

Understood, thanks!

though I am still figuring out on the map[0]=1 part but surely the rest of the part was indeed clear. thanks for these videos.

@JUST_C0DE

5 ай бұрын

if you select no element in sub array then , map[0]=1

solution blew my mind

Thanks bhaiya, understood

you are awesome bhaiya...

Thank you Striver. I owe you❤

you are topG of DSA

Thanks for the help raj bhaiya

thanks really good explination

Why updating the map?? Can someone explain?

Understood 💯💯💯

It seems like you have edited your voice in the video and made it soft, I am missing that bold voice which is there in the DP playlist. Please don't edit your voice, you don't have to adjust yourself for us. We like the way you are, the original STRIVER🔥🔥

@takeUforward

Жыл бұрын

But we need to look at the future, we want to go global, so audio quality has to be maintained, I hope you get that :)

@abdulrehmaan153

Жыл бұрын

​@@takeUforwardand we love you for that too, It's sort of unconditional 😂

Understood Sir!

Thanks bro. Understood

Understood ❤️

Nice explation ❤

Why initialize map with 1,0 in the beginning?

Please also make video for count pairs with given sum and divisible by k

Striver you can make these playlists a bit fun if you allow your viewers to suggest you problems they think discussable !! btw loving the playlist

@abdulrehmaan153

Жыл бұрын

Plz don't ruin it for us 😂😂😂

@dogwoofwoof8154

11 ай бұрын

plz no

Awesome explanation, one approach of sliding window will not work in this problem if array contains negative elements also.

What if the array contains 0s?

understood , but took tom much time to understood how to update the frequency if there exist a prefix sum in the HashMap

Can you pls pls plsssss do strings before binary search next plsss🙏 ? From 2023 batch🥺. Wish we could have the entire series in our 1st 2nd 3rd yrs

why can't the map be incremented before computing the count ???

Understood!

Understood✅🔥🔥

very nice. .thankyou

Regarding putting (0,1) int the Hashmap initally : Let consider somehow the preSum got exactly equal to our k, means now the sub-array till that presum element gives us the k (~ preSum-k = 0). means whenever we find our preSum touching the k value, we need to increment count but we will not be able to find it in hashMap as it is yet to be inserted that why either increment count based on if preSum-k = 0 or put a (0,1) in hashmap to automatically finding preSum-k = 0 in the hashMap. int preSum = 0, count = 0, start = 0; Map mp = new HashMap(); for(int i=0;i

Awesome Awesome Sir...............

understood striver thanks

Understood !! 😍😍

Thank you!!

nice ..........explanation

i still don't get the significance of (0,1) in the map, my answer still got submitted in Leetcode.

we can also use sliding window 2 pointer approach for this one code-> int findAllSubarraysWithGivenSum(vector & arr, int k) { int n =arr.size(),sum = 0,cnt = 0,left = 0; for(int right = 0;right k) sum-=arr[left++]; if(sum == k) cnt++; } return cnt; }

@amitranjan6998

10 ай бұрын

It will fail .arr[]=[1] k=0

@mriduljain1981

10 ай бұрын

@@amitranjan6998 yes we just need to add a condition of left

thank you so much

We can also solve this problem in O(1) space complexity but the T.C will be 2N using two pointer approach.

mpp[0] = 1 helps us to take the count when (sum == k ). Because when sum will be k, then remove will be 0. And then mpp[1] will give us 0, which will be added to the count. If we don't store 0 to our map. then we need to handle the case in an extra if condtion. which is if(sum == k) count++;

Understood 🎉

Bhaiya ye Question ka video dekhne se phale hoo gaya 😁😁Only Minor change int findAllSubarraysWithGivenSum(vector & nums, int k) { int right = 0; int left = 0; int count = 0; long long sum = nums[0]; int n = nums.size(); while(right while(left k){ sum = sum - nums[left]; left++; } if(sum == k){ count++; } right++; if(right sum+=nums[right]; } } return count; }

Understood ❤

Storing (0,1) in the hashmap is bit confusing, instead we can just increase a check i.e. if(currSum == k) count++. The more readable code(JAVA) will look like this: public int subarraySum(int[] nums, int k) { int currSum = 0, count = 0; int n = nums.length; HashMap map = new HashMap(); for(int i=0; i

Understood❤❤

Why cant we use sliding window approach here

Hey Strivers Good explanation ❤ Can you just change the gfg link of this question it redirect to same page. Once again thank you 👍

The Best♥

underrstood

❓ You mentioned performing a dry run on the array [3, -3, 1, 1, 1] to understand the significance of initially putting (0, 1) in the map. However, it hasn't been specified which sum we should consider for this particular dry run.

@sahilnayak9000

6 ай бұрын

Although i understood, if we didn't want to put initially that or if we find it challenging to understand its significance. there is an alternative approach to handle the situation. Another way is when currentSum - given_sum == 0 we just need to increment counter. that's it we can omit to put initially (0,1) pair in map.

UNDERSTOOD

Understood😁😉

understood!!!

Without adding to map, you need to count occurrences still not in map public int subarraySum(int[] nums, int k) { int sum=0; int count =0; Map map = new HashMap(); for(int i=0;i

Understood

thank you

Amazing

Understood.

understood