Anjali Kumari on Instagram: "When to use which approach in subarray problems: Sliding Window • Elements are non-negative • You need subarray sum / max / min • Window can expand and shrink predictably Kadane’s Algorithm • Elements can be positive or negative • You need the maximum subarray sum • Subarray must be contiguous HashMap (Prefix Sum) • Elements can be positive, negative, or zero • You need an exact target sum • Counting subarrays or checking existence is required Different problems need