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String / Sliding Window•Pattern: Fixed Sliding Window•Medium

Find all anagrams of P in S

Problem Intuition & Objective

Return all starting indices of P's anagrams in S using a fixed-size sliding window.

Time ComplexityO(|S|)
Optimal
Space ComplexityO(1) (26 chars)
Memory Bounds
Optimal Algorithmic Approach

Fixed-size sliding window with frequency diff counter.

Core Invariants & Edge Cases

  • Fixed window of size len(P) with character frequency comparison
  • Slide the window, adding new char and removing old char
  • Use a 'matches' counter to avoid full-array comparison each step
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