2012 ToT Spring Junior A p4 +, - into a nxn table, n steps
Source:
March 4, 2020
combinatoricssquare tabletableSigns
Problem Statement
Each entry in an n\times n table is either or . At each step, one can choose a row or a column and reverse all signs in it. From the initial position, it is possible to obtain the table in which all signs are . Prove that this can be accomplished in at most steps.