thanks xpi0t0s and shabbir..............

actually i view the tic tac to game table as a graph, where each block is a vertex of a graph and the all possible paths are connected to it
ex: there is edge between 1 to 9 , 1 to 5 , 1 to 3, 1 to 2 , 1 to 7 , 1 to 4 etc.

so the ADJACENCY LIST of graph is :

1=> 5 -> 9 -> 2 -> 3 -> 4 -> 7
2 => 5 -> 8 -> 1 -> 3
3 => 5 -> 7 -> 1 -> 2 ->6 ->9
4 => 4 -> 5 -> 6 -> 1 -> 7
5 => 2-> 8 -> 4 -> 6 -> 1 -> 9 -> 3 -> 7
6 => 5 -> 4 -> 3 -> 9
7 => 5 -> 3 -> 4 -> 1 -> 8 -> 9
8 => 5 -> 2 -> 7 -> 9
9 => 5 -> 1 -> 6 -> 3 -> 8 -> 7

win:
when user or comp. select 1 then his wining chances are:
he all ready taken (5, 9) or (2, 3) or ( 4 ,7)

comp next move:
if user has taken 2 successive places, then put X on the 3rd place.