No Four in a Row
Place either an ’X’ or an ’O’ into each empty cell such that four consecutive ’X’s or ’O’s do not appear horizontally, vertically or diagonally.
(Rules and example from WPC 2014)
- In theory, substituting four-in-a-row constraint with any-number-in-a-row constraint works. Most commonly, the number is either 3 or 4.
- Binaire, Binoxxo, Tic-Tac-Logic, Takuzu, etc are all names given to a variant of No Three in a Row with an additional constraint that (i) in each row/column, number of X's and O's are the same and (ii) no two rows/columns are identical. This variant has been independently invented multiple times circa late 2000s, for example Binaire was patented by Frank Coussement and Peter De Schepper (Belgium) in 2009.
History of the puzzle
Tic-Tac-Toe (American) or Noughts and Crosses (British) is a game that has been played at least since the Roman times.