Status: IN
`numSpecial` precomputes per-row and per-column sums in O(m·n), reducing the per-cell special check from O(m+n) to O(1) — this precomputation pattern recurs across matrix problems like `lucky-numbers-in-a-matrix` and `image-smoother`.
Source: entries/2026/06/06/special-positions-in-a-binary-matrix-solution.md