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n-1 cells of 0 and 1 in n x n table - All-Russian MO 1998 Regional (R4) 11.4

Source:

September 17, 2024
combinatorics

Problem Statement

There is an n×nn \times n table with n1n -1 cells containing ones and the remaining cells containing zeros. You can do this with the table the following operation: select the tap hole, subtract from the number in this cell, one, and to all other numbers on the same line or in the same column as the selected cell, add one. Is it possible from of this table, using the specified operations, obtain a table in which all numbers are equal?