Rooks Threatening Each Other
Source: Iran 3rd round 2013- Combinatorics exam problem 2
September 18, 2014
modular arithmeticcombinatorics unsolvedcombinatorics
Problem Statement
How many rooks can be placed in an chessboard such that each rook is threatened by at most rooks?
(15 points)
Proposed by Mostafa Einollah zadeh