June 2018 Update

Task/Tic-tac-toe/Fortran/tic-tac-toe.f

@@ -0,0 +1,99 @@
+! This is a fortran95 implementation of the game of tic-tac-toe.
+! - Objective was to use less than 100 lines.
+! - No attention has been devoted to efficiency.
+! - Indentation by findent: https://sourceforge.net/projects/findent/
+! - This is free software, use as you like at own risk.
+! - Compile: gfortran -o tictactoe tictactoe.f90
+! - Run: ./tictactoe
+! Comments to: wvermin at gmail dot com
+module tic
+   implicit none
+   integer :: b(9)
+contains
+   logical function iswin(p)
+      integer,intent(in) :: p
+      iswin = &
+         all(b([1,2,3])==p).or.all(b([4,5,6])==p).or.all(b([7,8,9])==p).or.&
+         all(b([1,4,7])==p).or.all(b([2,5,8])==p).or.all(b([3,6,9])==p).or.&
+         all(b([1,5,9])==p).or.all(b([3,5,7])==p)
+   end function iswin
+   subroutine printb(mes)
+      character(len=*) :: mes
+      integer          :: i,j
+      character        :: s(0:2) = ['.','X','O']
+      print "(3a3,'   ',3i3)",(s(b(3*i+1:3*i+3)),(j,j=3*i+1,3*i+3),i=0,2)
+      if(mes /= ' ') print "(/,a)",mes
+   end subroutine printb
+   integer recursive function minmax(player,bestm) result(bestv)
+      integer :: player,bestm,move,v,bm,win=1000,inf=100000
+      real    :: x
+      if (all(b .ne. 0)) then
+         bestv = 0
+      else
+         bestv = -inf
+         do move=1,9
+            if (b(move) == 0) then
+               b(move) = player
+               if (iswin(player)) then
+                  v = win
+               else
+                  call random_number(x)
+                  v = -minmax(3-player,bm) - int(10*x)
+               endif
+               if (v > bestv) then
+                  bestv = v
+                  bestm = move
+               endif
+               b(move) = 0
+               if (v == win) exit
+            endif
+         enddo
+      endif
+   end function minmax
+end module tic
+program tictactoe
+   ! computer: player=1, user: player=2
+   use tic
+   implicit none
+   integer :: move,ios,v,bestmove,ply,player=2,k,values(8)
+   integer,allocatable :: seed(:)
+   call date_and_time(values=values)
+   call random_seed(size=k)
+   allocate(seed(k))
+   seed = values(8)+1000*values(7)+60*1000*values(6)+60*60*1000*values(5)
+   call random_seed(put=seed)
+   mainloop: do
+      b = 0
+      call printb('You have O, I have X. You enter 0: game ends.')
+      plyloop: do ply=0,4
+         if (player == 2 .or. ply >0 ) then  ! user move
+            write(*,"(/,a)",advance='no'),'Your move? (0..9) '
+            getloop: do
+               readloop: do
+                  read (*,*,iostat=ios),move
+                  if (ios == 0 .and. move  >= 0 .and. move <= 9) exit readloop
+                  write(*,"(a)",advance='no'),'huh? Try again (0..9): '
+               enddo readloop
+               if (  move  == 0) exit mainloop
+               if (b(move) == 0) exit getloop
+               write(*,"(a)",advance='no'),'Already occupied, again (0..9): '
+            enddo getloop
+            b(move) = 2
+            if(iswin(2)) then   ! this should not happen
+               call printb('***** You win *****')
+               exit plyloop
+            endif
+         endif
+         v = minmax(1,bestmove)   ! computer move
+         b(bestmove) = 1
+         if(iswin(1)) then
+            call printb('***** I win *****')
+            exit plyloop
+         endif
+         write(*,"(/,a,i3)"), 'My move: ',bestmove
+         call printb(' ')
+      enddo plyloop
+      if(ply == 5) write(*,"('***** Draw *****',/)")
+      player = 3-player
+   enddo mainloop
+end program