Nine cards numbered 1 through 9 are kept facing up on a table. Alice and Bob are playing a game wherein they pick up cards one at a time, alternatively. The first person to have three cards with sum 15 wins the game.
Further, it is upto Bob to choose who picks the first card. Can Bob ensure a win?
(7, 8) is not a winning hand, because two cards have a sum 15
(1,2,3,9) is not a winning hand because four cards have sum 15
(2, 6, 3, 7) is a winning hand because three cards(2, 6, 7) have sum 15