Tic Tac Toe game implementation using minimax algortihm

In a Tic Tac Toe game two players, X and O, take turns to mark the spaces in a 3X3 grid. The winner will be the player who first succeeds in placing three of his/her marks in a horizontal, vertical, or diagonal row. This is a program for a computer (X player) to play with a human (O player) on Tic Tac Toe game given an initial status of the game. The initial status of the game is represented by a string of 9 characters. For example, the game status can be expressed using string “OOO_OX_XX". The program always plays the winning strategies and try to defeat the human player if possible. The program tries to play a maxmin strategy first. If the maxmin strategy is not beneficial it will play a minmax strategy to minimize the payoff of the other player.

The sample input and output are shown below: Example 1: "XXO_O_XO_" The computer chooses to fill the cell #4 1 X X O X O X O The Computer Won! Example 2: "XXOOO_X__" The computer chooses to fill the cell #6 X X O O O X X Human player please select a cell number to fill: 1 Not a valid move, please try again. Please select a cell to fill: 8 Thanks. Now the board looks like: X X O O O X X O The computer chooses to fill the cell #9 X X O O O X X O X The game is finished. No one won the game.