2021 USAMO Problems/Problem 3
Revision as of 06:19, 18 July 2021 by Satisfiedmagma (talk | contribs)
Let be an integer. An board is initially empty. Each minute, you may perform one of three moves:
[list]
[*] If there is an L-shaped tromino region of three cells without stones on the board (see figure; rotations not allowed), you may place a stone in each of those cells.
[*] If all cells in a column have a stone, you may remove all stones from that column.
[*] If all cells in a row have a stone, you may remove all stones from that row.