# Tic-tac-toe checking **URL:** \ **Category:** ruby-talk\ **Created:** [17 October 2005 14:17 UTC](https://rubytalk.org/t/tic-tac-toe-checking/21610 "2005-10-17T14:17:12Z")\ **Posts on this page:** 1\ **Page:** 1
**Author:** ![Brown\_Warren](https://avatars.discourse-cdn.com/v4/letter/b/73ab20/32.png) [@Brown\_Warren](https://rubytalk.org/u/Brown_Warren)\ **Post date:** [17 October 2005 14:17 UTC](https://rubytalk.org/t/tic-tac-toe-checking/21610/1 "2005-10-17T14:17:12Z")
CBlair1986, > I'd like to be able to check for a X-in-a-row win on a > Y-by-Y board. I'd eventually like to be able to check > for a 10-in-a-row on a 50-by-50 board. Are there any > easy methods I could use, besides doing a check for > each possible win?     Well, if you only need to check for a win after someone moves, you can just perform four checks for the up/down/diagonal1/diagonal2 cases for up to X squares away from the last move.     If instead you don't know the last move and need a generic algorithm to see if player A has a win, a simple one is to initialize a YxY array to zeros, then loop over each row/column. For each square where player A has played, increment the four squares: same row next column; next row previous column; next row same column; and next row next column. Or, put another way: 123 456 789     If player A has played in square 5, increment squares 6, 7, 8, and 9. After each increment, test for a value equal to X, indicating a player A win. If you need to check for a player B win, you'll need to use the same algorithm on a separate array. If you have a player C, you'll need a third array, etc.     This algorithm is O(Y^2), so it won't scale well when Y becomes large, but for a 50x50 board, your only talking about 2,500 iterations, which should be fine.     I hope this helps.     - Warren Brown