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$ curl repovive.com/roadmaps/data-structures/sqrt-decomposition/range-sum-implementation

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$ curl repovive.com/roadmaps/data-structures/sqrt-decomposition/range-sum-implementation

Repovive

Range Sum - Implementation - Sqrt Decomposition | Data Structures | Repovive

Repovive.

Data Structures19 sections · 729 units49h total

Open in Course

Range Sum - Implementation

The code

Here's the range sum query:

function rangeSum(l, r, arr, blockSum, B)
 blockL := floor(l / B)
 blockR := floor(r / B)

 if blockL = blockR then
 // Same block - iterate directly
 sum := 0
 for i from l to r
 sum := sum + arr[i]
 return sum

 sum := 0
 // Left tail
 for i from l to (blockL + 1) * B - 1
 sum := sum + arr[i]

 // Complete blocks
 for b from blockL + 1 to blockR - 1
 sum := sum + blockSum[b]

 // Right tail
 for i from blockR * B to r
 sum := sum + arr[i]

 return sum

Time: $O(\sqrt{n})$ . Space: $O(\sqrt{n})$ for block sums.