MathDB

11.2

Part of 2009 All-Russian Olympiad Regional Round

Problems(1)

X' - O in 10 x10 board

Source: All-Russian MO 2009 Regional 11. 2

8/28/2024
In some cells of the table 10×1010\times 10 arranged several XX's and a few OO's. It is known that there is no line (row or column) completely filled with identical symbols (crosses or zeros). However, if in any empty If you place any icon in a cell, this condition will be violated. What is the minimum number of icons that can appear in a table?
combinatorics