Any idea how to solve it?
or please just explain the case following:
50 50 50
50 50 50
50 50 50
50 50 50
50 50 50
50 50 50
47.46
thx in advance!
11229 - Improved tic-tac-toe.
Moderator: Board moderators
This means:They know that who plays first has a better chance to win, so they always try to win when playing first and try not to loose when playing second.
First player chooses the mass which leads first player's win with the highest probability.Second player chooses the opposite.
I think this phrase will naturally lead you to the algorithm ...
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Rio
Well, what is natural for some people is not natural for others 
I started doing these probability/game questions recently and took me a while to grasp the concept. It does not help that I just can't think recursively. I recommend going through "Understanding Probabilities" tutorial at TopCoder (I haven't finished those problems yet, and I should).
In this specific case - you can consider a tie to be a win for the second player. That is why you get <50% for that board. And, note that in the case of a tie, first player made the last move.
I started doing these probability/game questions recently and took me a while to grasp the concept. It does not help that I just can't think recursively. I recommend going through "Understanding Probabilities" tutorial at TopCoder (I haven't finished those problems yet, and I should).
In this specific case - you can consider a tie to be a win for the second player. That is why you get <50% for that board. And, note that in the case of a tie, first player made the last move.