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110i

121

I'm kind of bummed that I didn't find a beautiful one-line solution using FIND FIRST, but it just gives the value it finds, not the position in the list, which is what we need to find the line endpoints in WIN LINES. So it's a plain old fashioned FOR loop.

playingfalseDCSCHplayingfalseX's turn?

available squaresavailable squares1

5.6.3.5

5.6.3.7

5.6.4.2

This is a place where students are likely to use an unnecessary IF/ELSE block because the solution above seems "too easy" and therefore suspicious. Ideally they should both understand that their solution is correct if it works -- there isn't only one "right" way to write a program -- and that composition of functions enables fairly complicated algorithms to be one-liners when actually coded.

5.6.4.3

XSecond rule: block opponent's win.

Fallback: move somewhere!

helper for 5.6.3.7

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