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title: 'Arrays - Prefix sum, carry forward & Subarrays (Quick revision) '

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The following video provides a concise summary of the **Prefix sum** class. Whether you're new to the concept or looking for a quick refresher, this video is your go-to source for understanding prefix sums. Dive in and enhance your knowledge!



>https://www.scaler.com/meetings/dsa-prefixsum-revision-3/j/a/V2@-_JnCX8eKhHnv4nk-Y1SD_bOprQ_0



*You need only **26 minutes** to complete the below mentioned topics through this revision video!!*


1. Range Sum Query
2. Even Number in a Range
3. Sum of Even Elements in given Range
4. When to use Prefix Sum?"



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Within the following video lies the essence of the **Carry Forward** class. Let the knowledge ripple through your mind like a stone cast into a calm pond. Watch, learn, and let your curiosity carry you forward!
>https://www.scaler.com/meetings/dsa-carryforward-revision-20/j/a/-IriDH-$iaRihPXf1NnW5@Sv6N9n6R0M

*You need only **24 minutes** to complete the below mentioned topics through this revision video!!*


1. Count ```ag``` pairs
2. Leaders in an array
3. When to use Carry Forward?"



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This video provides a brief **Introduction to subarrays**. If you're new to this topic or looking for a quick overview, this video is your perfect starting point. Enjoy and learn!
>https://www.scaler.com/meetings/dsa-subarrays-1-revision-5/j/a/D2QAhF3j3L-WQhqRttS6iqygoDQyLaJe

*You need only **27 minutes** to complete the below mentioned topics through this revision video!!*


1. Subarray Intro and Properties
2. Printing all Subarrays
3. Printing all Subarray Sums
4. General Subarray Questions



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With the help of following video, get ready to supercharge your understanding of the **Contribution technique and sliding window** method! It's your express ticket to do a quick revision. 
 
>https://www.scaler.com/meetings/dsa-subarrays-2-revision-4/j/a/V@WWQruUZ230zsX9J@n-qFiVzNgomTuJ

*You need only **29 minutes** to complete the below mentioned topics through this revision video!!*

1. Sum of all Subarray Sums :
Contribution Tecnhique
2. Max Subarray Sum of len = k : 
Sliding Window Techhnique



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We've crafted these special videos with the utmost care and dedication to support our learners in their revision before the contest. We encourage you to make the most of these resources, allowing them to boost your confidence and readiness for the upcoming challenge. You've got this, and we're here to help you shine in the contest. 💎🚀