## Friday, May 29, 2015

### How to Never Lose a Game of Tic-Tac-Toe

There are many places on the internet that show you how to never lose a game of Tic-Tac-Toe. One of my favorites is Quora. You can click on it for FULL directions, including pictures. I'll go over some highlights.
IF YOU GO FIRST...Avoid placing your first piece on an edge square, and keep it on the center or a corner square. Placing it on an edge square will give your opponent the advantage.

IF YOUR OPPONENT GOES FIRST...Unfortunately, if your opponent goes first and uses all the above techniques, there's no way that you can win. In fact, the only way you can win is if his/her first move is an edge piece.

After the first moves by both players, you can follow the list below. Do the first thing on the list that you are able to do.

Win: If you have two in a row, you can place a third to get three in a row.
Block: If your opponent has two in a row, you must play the third to block your opponent.
Fork: Create an opportunity where you have two threats to win (two non-blocked lines of 2).
Blocking an opponent's fork:
Option 1: You should create two in a row to force your opponent into defending, as long as it doesn't result in them creating a fork. For example, if "X" has a corner, "O" has the center, and "X" has the opposite corner as well, "O" must not play a corner in order to win. (Playing a corner in this scenario creates a fork for "X" to win.)
Option 2: If there is a configuration where the opponent can fork, you should block that fork.
Center:  Mark the center. (If it is the first move of the game, playing on a corner gives "O" more opportunities to make a mistake and may therefore be the better choice; however, it makes no difference between perfect players.)
Opposite corner: If the opponent is in the corner, the player plays the opposite corner.
Empty corner: The player plays in a corner square.
Empty side: The player plays in a middle square on any of the 4 sides.

Notes:
The above list is the programming for the first computer tic-tac-toe game. In 1952, OXO (or Noughts and Crosses, the English name for tic-tac-toe) for the EDSAC computer became one of the first known video games. The computer player could play perfect games of tic-tac-toe against a human opponent.

Bonus:
Can anyone comment on what a nought is?﻿