GridWits

Visible-Count Bound

Medium Used by Smart Hint

A clue of k means the tallest building can't sit within the first k-1 cells from that edge — eliminate it there.

1 2 3 4 1 2 3 4 3

How it works

  1. The 3 on the left says three buildings are visible along this row.
  2. Once the tallest (4) appears, nothing behind it shows — so all three visible buildings must appear by the 4's own position.
  3. If the 4 sat in the first or second cell, at most one or two buildings could show. Strike 4 from both.