Task: Tic-tac-toe

C: #include <stdio.h>
#include <stdlib.h>

int b[3][3]; 

int check_winner()
{
	int i;
	for (i = 0; i < 3; i++) {
		if (b[i][0] && b[i][1] == b[i][0] && b[i][2] == b[i][0])
			return b[i][0];
		if (b[0][i] && b[1][i] == b[0][i] && b[2][i] == b[0][i])
			return b[0][i];
	}
	if (!b[1][1]) return 0;

	if (b[1][1] == b[0][0] && b[2][2] == b[0][0]) return b[0][0];
	if (b[1][1] == b[2][0] && b[0][2] == b[1][1]) return b[1][1];

	return 0;
}

void showboard()
{
	const char *t = "X O";
	int i, j;
	for (i = 0; i < 3; i++, putchar('\n'))
		for (j = 0; j < 3; j++)
			printf("%c ", t[ b[i][j] + 1 ]);
	printf("-----\n");
}

#define for_ij for (i = 0; i < 3; i++) for (j = 0; j < 3; j++)
int best_i, best_j;
int test_move(int val, int depth)
{
	int i, j, score;
	int best = -1, changed = 0;

	if ((score = check_winner())) return (score == val) ? 1 : -1;

	for_ij {
		if (b[i][j]) continue;

		changed = b[i][j] = val;
		score = -test_move(-val, depth + 1);
		b[i][j] = 0;

		if (score <= best) continue;
		if (!depth) {
			best_i = i;
			best_j = j;
		}
		best = score;
	}

	return changed ? best : 0;
}

const char* game(int user)
{
	int i, j, k, move, win = 0;
	for_ij b[i][j] = 0;

	printf("Board postions are numbered so:\n1 2 3\n4 5 6\n7 8 9\n");
	printf("You have O, I have X.\n\n");
	for (k = 0; k < 9; k++, user = !user) {
		while(user) {
			printf("your move: ");
			if (!scanf("%d", &move)) {
				scanf("%*s");
				continue;
			}
			if (--move < 0 || move >= 9) continue;
			if (b[i = move / 3][j = move % 3]) continue;

			b[i][j] = 1;
			break;
		}
		if (!user) {
			if (!k) { 
				best_i = rand() % 3;
				best_j = rand() % 3;
			} else
				test_move(-1, 0);

			b[best_i][best_j] = -1;
			printf("My move: %d\n", best_i * 3 + best_j + 1);
		}

		showboard();
		if ((win = check_winner())) 
			return win == 1 ? "You win.\n\n": "I win.\n\n";
	}
	return "A draw.\n\n";
}

int main()
{
	int first = 0;
	while (1) printf("%s", game(first = !first));
	return 0;
}











Ada: with Ada.Text_IO, Ada.Numerics.Discrete_Random;
  
  

procedure Tic_Tac_Toe is

   type The_Range is range 1 .. 3;
   type Board_Type is array (The_Range, The_Range) of Character;

   package Rand is new Ada.Numerics.Discrete_Random(The_Range);
   Gen: Rand.Generator; 

   procedure Show_Board(Board: Board_Type) is
      use Ada.Text_IO;
   begin
      for Row in The_Range loop
         for Column in The_Range loop
            Put(Board(Row, Column));
         end loop;
         Put_Line("");
      end loop;
      Put_Line("");
   end Show_Board;

   function Find_Winner(Board: Board_Type) return Character is
      

      function Three_Equal(A,B,C: Character) return Boolean is
      begin
         return (A=B) and (A=C);
      end Three_Equal;

   begin 
      for I in The_Range loop
         if    Three_Equal(Board(I,1), Board(I,2), Board(I,3)) then
            return Board(I,1);
         elsif  Three_Equal(Board(1,I), Board(2,I), Board(3,I)) then
            return Board(1,I);
         end if;
      end loop;
      if Three_Equal(Board(1,1), Board(2,2), Board (3,3)) or
         Three_Equal(Board(3,1), Board(2,2), Board (1,3)) then
         return Board(2,2);
      end if;
      return ' ';
   end Find_Winner;

   procedure Do_Move(Board: in out Board_Type;
                     New_Char: Character; Computer_Move: Boolean) is
      Done: Boolean := False;
      C: Character;
      use Ada.Text_IO;

      procedure Do_C_Move(Board: in out Board_Type; New_Char: Character) is
         Found: Boolean := False;
         X,Y: The_Range;
      begin
         while not Found loop
            X := Rand.Random(Gen);
            Y := Rand.Random(Gen);
            if (Board(X,Y) /= 'x') and  (Board(X,Y) /= 'o') then
               Found := True;
               Board(X,Y) := New_Char;
            end if;
         end loop;
      end Do_C_Move;

   begin
      if Computer_Move then
         Do_C_Move(Board, New_Char);
      else 
         Put_Line("Choose your move, " & New_Char);
         while not Done loop
            Get(C);
            for Row in The_Range loop
               for Col in The_Range loop
                  if Board(Row, Col) = C then
                     Board(Row, Col) := New_Char;
                     Done := True;
                  end if;
               end loop;
            end loop;
         end loop;
      end if;
   end Do_Move;

   The_Board : Board_Type := (('1','2','3'), ('4','5','6'), ('7','8','9'));
   Cnt_Moves: Natural := 0;
   Players: array(0 .. 1) of Character := ('x', 'o'); 
   C_Player: array(0 .. 1) of Boolean := (False, False);
   Reply: Character;

begin 

   
   for I in Players'Range loop
      Ada.Text_IO.Put_Line("Shall " & Players(I) &
                             " be run by the computer? (y=yes)");
      Ada.Text_IO.Get(Reply);
      if Reply='y' or Reply='Y' then
         C_Player(I) := True;
         Ada.Text_IO.Put_Line("Yes!");
      else
         Ada.Text_IO.Put_Line("No!");
      end if;
   end loop;
   Rand.Reset(Gen); 

   
   while (Find_Winner(The_Board) = ' ') and (Cnt_Moves < 9) loop
      Show_Board(The_Board);
      Do_Move(The_Board, Players(Cnt_Moves mod 2), C_Player(Cnt_Moves mod 2));
      Cnt_Moves := Cnt_Moves + 1;
   end loop;
   Ada.Text_IO.Put_Line("This is the end!");

   
   Show_Board (The_Board);
   if Find_Winner(The_Board) = ' ' then
      Ada.Text_IO.Put_Line("Draw");
   else
      Ada.Text_IO.Put_Line("The winner is: " & Find_Winner(The_Board));
   end if;
end Tic_Tac_Toe;