CustomCC0-1.0#P0071800
Unique Value Submatrix Count
Summary
- •Phase 2 / 2D Sliding Window, Hashing
- •Reasoning-first competitive programming drill
Problem Description
Given a grid of size N x M, count the number of submatrices (rectangular subgrids) in which all elements are unique.
How to read this problem in plain language:
- This is a Phase 2 reasoning drill focused on 2D Sliding Window, Hashing.
- Typical lenses to test first: 2d array, counting, hash.
- Constraints reminder: 1 ≤ N,, 1 ≤ grid[i][j] ≤ 1e6
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,, 1 ≤ grid[i][j] ≤ 1e6
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.
2d arraycountinghash