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3 in a row = bad (Posted on 2006-04-26) Difficulty: 4 of 5
For n=3,4,5,6,7,8 find:

a) The minimum number of counters that need be placed on a nxn chessboard such that no additional counters can be placed without creating any straight line of 3;

b) The maximum number of counters that can be placed on a nxn chessboard such that no three lie in a straight line.

Remember that positions like A1, B3, and C5 are in a straight line.
(Try to continue the sequences if you can)

See The Solution Submitted by Jer    
Rating: 4.5000 (2 votes)

Comments: ( Back to comment list | You must be logged in to post comments.)
Some Thoughts re: so far... Comment 13 of 13 |
(In reply to so far... by Josh)

Good job Josh!

When I saw the "triangle" formation of the counters in my own 5x5, seeing how the tight group reduced the number of lines restricting the placement of other counters, I thought it might work for other grids too.  I just did not have the time to explore it.  Of course, it did not help that my own 5x5 grid could only support 9 counters.  Below is the 8x8 with n*2 = 16 counters.

8x8______MAX=16
. . X . X . . .
. . . X . X . .
. X . . . . . X
X . . . . . X .
. X . . . . . X
X . . . . . X .
. . X . X . . .
. . . X . X . .

Edited on April 28, 2006, 6:12 am
  Posted by Dej Mar on 2006-04-28 04:23:40

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