[Fix #108] Added Optimized Solutions for Range Sum Query and Subarray Sum Count

[Krishna200608]

Issue: #108

Summary

Added two well-structured and well-documented C++ solutions that demonstrate core Prefix Sum techniques under
algos/range_queries/prefixSum/soln/.

• Solution1.cpp
  Implements efficient range sum queries using prefix sums, achieving
  O(N) preprocessing time and O(1) time per query.

• Solution2.cpp
  Solves the problem of counting subarrays with a given sum using a combination of
  prefix sums and hashing, with an overall O(N) time complexity.

Both solutions include:

• Clear and concise problem statements
• Step-by-step explanations of the approach
• Detailed time and space complexity analysis

All files compile successfully and are organized for readability, learning, and reuse.

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Proof of Correctness (Codeforces Submissions)

Problem: Codeforces 1605B — Reverse Sort
Submission Link: https://codeforces.com/contest/1605/submission/356073603

Problem: Codeforces 1843E — Tracking Segments
Submission Link: https://codeforces.com/contest/1843/submission/356073814

[OpenGitBot]

Hey @Krishna200608

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

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