Implemented Easy Prefix Sum Solutions (Issue #12)

[adityashirsatrao007]

Issue : #12

Added solutions for Range Sum Query - Immutable and Running Sum of 1d Array

[OpenGitBot]

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PR Template is not followed. Kindly follow the template & edit it again for consideration as a valid pull request.

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Correct Tempelate:
Issue : #<Issue_Number>

[Copilot]

Pull request overview

This PR adds two C++ solutions for prefix sum problems as part of Issue #12: Running Sum of 1d Array (LeetCode 1480) and Range Sum Query - Immutable (LeetCode 303). Both implementations use the prefix sum technique to efficiently compute cumulative sums.

Key Changes:

• Added RunningSum1dArray.cpp implementing a running sum calculator using prefix sum approach
• Added RangeSumQueryImmutable.cpp implementing a range sum query class with O(1) query time

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 5 comments.

File	Description
RunningSum1dArray.cpp	Implements running sum using prefix sum technique with O(N) time complexity
RangeSumQueryImmutable.cpp	Implements range sum queries using precomputed prefix sum array with O(1) query time

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[adityashirsatrao007]

Apologies for the oversight. I have updated the PR description to strictly follow the required template format.

[OpenGitBot]

Hey @adityashirsatrao007

Thanks for opening this PR 🚀. Mentor will review your pull request soon and till then, keep contributing and stay calm.

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[OpenGitBot]

Hey @adityashirsatrao007

Your PR has been merged 🥳🥳 and you have earned 20 points.

Thanks for contributing in OpenCode'25✨✨