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$ curl repovive.com/roadmaps/data-structures/arrays-prefix-sums/range-sum-implementation

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$ curl repovive.com/roadmaps/data-structures/arrays-prefix-sums/range-sum-implementation

Repovive

Range Sum - Implementation - Arrays & Prefix Sums | Data Structures | Repovive

Repovive.

Data Structures19 sections · 729 units49h total

Open in Course

Range Sum - Implementation

Complete solution

Here's the full solution:

class NumArray
    prefix := empty array

    function init(nums)
        n := length of nums
        prefix := array of size (n + 1)
        prefix[0] := 0
        for i from 0 to n - 1
            prefix[i + 1] := prefix[i] + nums[i]

    function sumRange(left, right)
        return prefix[right + 1] - prefix[left]

Initialization: $O(n)$ time, $O(n)$ space. Each query: $O(1)$ time.