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Subarray Product with Modulo

Thinking Mode

Summary

  • •Phase 1 / number_theory, sliding_window
  • •Reasoning-first competitive programming drill

Problem Description

Given an array of n positive integers and an integer m, count the number of subarrays whose product is divisible by m. How to read this problem in plain language: - This is a Phase 1 reasoning drill focused on numbert​heory, slidingw​indow. - Typical lenses to test first: number theory, arrays, sliding window. - Constraints reminder: 1 ≤ n≤2×105, 1 ≤ m≤106, 1 ≤ ai​≤109 Mini examples for mental simulation: 1) Boundary example: Describe why this case is tricky. Explain expected behavior and why naive logic may fail. 2) Adversarial example: Adversarial case where naive greedy/local decision looks correct but fails globally. Lite-mode writing target: - Write 1~2 observations that shrink the search space. - Name one final algorithm and state target complexity explicitly. - Validate with at least 2 edge cases and one hand simulation.

Constraints

  • •
    1 ≤ n≤2×105, 1 ≤ m≤106, 1 ≤ ai​≤109

Analysis

Key Insight

Use this hint to refine your reasoning. This step should reduce search space or formalize correctness. State why this insight changes your algorithm choice.

number theoryarrayssliding windowmultiplicative
number theoryarrayssliding windowmultiplicative