Minimax is an algorithm used to determine the score in a zero-sum game after a certain number of moves, with best play according to an evaluation function.

int maxi( int depth ) {
    if ( depth == 0 ) return evaluate();
    int max = -oo;
    for ( all moves) {
        score = mini( depth - 1 );
        if( score > max )
            max = score;
    }
    return max;
}
 
int mini( int depth ) {
    if ( depth == 0 ) return -evaluate();
    int min = +oo;
    for ( all moves) {
        score = maxi( depth - 1 );
        if( score < min )
            min = score;
    }
    return min;
}

http://web.archive.org/web/20120209041607/http://chessprogramming.wikispaces.com/Minimax