BEGIN

COMMENT scoreWin      6    ;
COMMENT scoreTie      5    ;
COMMENT scoreLose     4    ;
COMMENT scoreMax      9    ;
COMMENT scoreMin      2    ;
COMMENT scoreInvalid  0    ;
COMMENT pieceX        1    ;
COMMENT pieceY        2    ;
COMMENT pieceBlank    0    ;

INTEGER movecount;
INTEGER ARRAY board[0:8];

INTEGER PROCEDURE winner;
BEGIN
    INTEGER t, p;
  
    p := 0;
    t := board[ 0 ];
    IF 0 # t THEN BEGIN
        IF ( ( ( t = board[1] ) AND ( t = board[2] ) ) OR
             ( ( t = board[3] ) AND ( t = board[6] ) ) ) THEN
            p := t;
    END;
  
    IF 0 = p THEN BEGIN
        t := board[1];
        IF ( 0 # t ) AND ( t = board[4] ) AND ( t = board[7] ) THEN
            p := t
        ELSE BEGIN
            t := board[2];
            IF ( 0 # t ) AND ( t = board[5] ) AND ( t = board[8] ) THEN
                p := t
            ELSE BEGIN
                t := board[3];
                IF ( 0 # t ) AND ( t = board[4] ) AND ( t = board[5] ) THEN
                    p := t
                ELSE BEGIN
                    t := board[6];
                    IF ( 0 # t ) AND ( t = board[7] ) AND ( t = board[8] ) THEN
                        p := t
                    ELSE BEGIN
                        t := board[4];
                        IF ( 0 # t ) THEN BEGIN
                            IF ( ( ( t = board[0] ) AND ( t = board[8] ) ) OR
                                 ( ( t = board[2] ) AND ( t = board[6] ) ) ) THEN
                                p := t;
                        END;
                    END;
                END;
            END;
        END;
    END;
  
    winner := p;
END winner;

INTEGER PROCEDURE winner2( move );
    VALUE move;
    INTEGER move;
BEGIN
    INTEGER x;
    x := board[ move ];
    CASE move OF
    0:   BEGIN
        IF NOT ( ( ( x = board[1] ) AND ( x = board[2] ) ) OR
                 ( ( x = board[3] ) AND ( x = board[6] ) ) OR
                 ( ( x = board[4] ) AND ( x = board[8] ) ) )
            THEN x := 0;
        END;
    1:  BEGIN
        IF NOT ( ( ( x = board[0] ) AND ( x = board[2] ) ) OR
                 ( ( x = board[4] ) AND ( x = board[7] ) ) )
            THEN x := 0;
        END;
    2:  BEGIN
        x := board[ 2 ];
        IF NOT ( ( ( x = board[0] ) AND ( x = board[1] ) ) OR
                 ( ( x = board[5] ) AND ( x = board[8] ) ) OR
                 ( ( x = board[4] ) AND ( x = board[6] ) ) )
            THEN x := 0;
        END;
    3:  BEGIN
        x := board[ 3 ];
        IF NOT ( ( ( x = board[4] ) AND ( x = board[5] ) ) OR
                 ( ( x = board[0] ) AND ( x = board[6] ) ) )
            THEN x := 0;
        END;
    4:  BEGIN
        x := board[ 4 ];
        IF NOT ( ( ( x = board[0] ) AND ( x = board[8] ) ) OR
                 ( ( x = board[2] ) AND ( x = board[6] ) ) OR
                 ( ( x = board[1] ) AND ( x = board[7] ) ) OR
                 ( ( x = board[3] ) AND ( x = board[5] ) ) )
            THEN x := 0;
        END;
    5:  BEGIN
        x := board[ 5 ];
        IF NOT ( ( ( x = board[3] ) AND ( x = board[4] ) ) OR
                 ( ( x = board[2] ) AND ( x = board[8] ) ) )
            THEN x := 0;
        END;
    6:  BEGIN
        x := board[ 6 ];
        IF NOT ( ( ( x = board[7] ) AND ( x = board[8] ) ) OR
                 ( ( x = board[0] ) AND ( x = board[3] ) ) OR
                 ( ( x = board[4] ) AND ( x = board[2] ) ) )
            THEN x := 0;
        END;
    7:  BEGIN
        x := board[ 7 ];
        IF NOT ( ( ( x = board[6] ) AND ( x = board[8] ) ) OR
                 ( ( x = board[1] ) AND ( x = board[4] ) ) )
            THEN x := 0;
        END;
    8:  BEGIN
        x := board[ 8 ];
        IF NOT ( ( ( x = board[6] ) AND ( x = board[7] ) ) OR
                 ( ( x = board[2] ) AND ( x = board[5] ) ) OR
                 ( ( x = board[0] ) AND ( x = board[4] ) ) )
            THEN x := 0;
        END
    ELSE text( 1, "unexpected move" );

    winner2 := x;
END winner2;

INTEGER PROCEDURE minmax( alpha, beta, depth, move );
    VALUE alpha, beta, depth, move;
    INTEGER alpha, beta, depth, move;
BEGIN
    INTEGER value, p, score, pm;
    value := 0;
    movecount := movecount + 1;

    IF depth >= 4 THEN BEGIN
        p := winner2( move );
        IF p # 0 THEN BEGIN
            IF p = 1 THEN value := 6
            ELSE value := 4;
        END
        ELSE BEGIN
            IF depth = 8 THEN value := 5;
        END;
    END;

    IF value = 0 THEN BEGIN
        IF 1 = ( depth MOD 2 ) THEN BEGIN
            value := 2;
            pm := 1;
        END
        ELSE BEGIN
            value := 9;
            pm := 2;
        END;

        p := 0;
        WHILE p <= 8 DO BEGIN
            IF board[ p ] = 0 THEN BEGIN
                board[ p ] := pm;
                score := minmax( alpha, beta, depth + 1, p );
                board[ p ] := 0;
            
                IF pm = 1 THEN BEGIN
                    IF score > value THEN BEGIN
                        value := score;
                        IF ( ( value = 6 ) OR ( value >= beta ) ) THEN
                            p := 10
                        ELSE BEGIN
                            IF ( value > alpha ) THEN alpha := value;
                        END;
                    END;
                END
                ELSE BEGIN
                    IF score < value THEN BEGIN
                        value := score;
                        IF ( value = 4 ) OR ( value <= alpha ) THEN
                            p := 10
                        ELSE BEGIN
                            IF ( value < beta ) THEN beta := value;
                        END;
                    END;
                END;
            END;

            p := p + 1;
            END;
    END;

    minmax := value;
END minmax;

PROCEDURE findsolution( move );
    VALUE move;
    INTEGER move;
BEGIN
    INTEGER score;

    board[ move ] := 1;
    score := minmax( 2, 9, 0, move );
    board[ move ] := 0;
END findsolution;

PROCEDURE main;
BEGIN
    INTEGER i;
    
    FOR i:=0 STEP 1 UNTIL 8 DO BEGIN
        board[ i ] := 0;
    END;

    FOR i:=0 STEP 1 UNTIL 9 DO BEGIN
        movecount := 0;
        findsolution( 0 );
        findsolution( 1 );
        findsolution( 4 );
    END;

    text( 1, "moves: " );
    write( 1, movecount );
    text( 1, "*N" );
    
    ioc(22);
END main;

main;

END
FINISH