Square coloring

Task number: 3923

Consider a square grid \(21 \times 21\).

Show that one of the colors appears in at least three rows as well as in at least in three columns, if the cells of the grid are colored as follows:

  • Variant

    At most 5 different colors appear in each row and column.

  • Variant

    No more than 6 different colors in each column and row.

Difficulty level: Hard task
Proving or derivation task
Solution require uncommon idea
Cs translation
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