Solution to Towers of Hanoi :
program TowersofHanoi;
var
numdiscs : integer;
(******************************************************)
procedure DoTowers (NumDiscs,
OrigPeg, NewPeg, TempPeg : integer);
(* Explanation of variables:
Number of discs -- number of
discs on OrigPeg
OrigPeg -- peg number of the
tower
NewPeg -- peg number to move
the tower to
TempPeg -- peg to use for
temporary storage
*)
begin
(* Take care of the base case --
one disc *)
if NumDiscs = 1 then
writeln (OrigPeg, ' ---> ',
NewPeg)
(* Take care of all other cases
*)
else
begin
(* First, move all discs except the
bottom disc to TempPeg, using NewPeg
as the temporary peg for this
transfer *)
DoTowers (NumDiscs-1,
OrigPeg, TempPeg, NewPeg);
(* Now, move the bottommost disc
from OrigPeg to NewPeg *)
writeln (OrigPeg, ' ---> ',
NewPeg);
(* Finally, move the discs which are
currently on TempPeg to NewPeg,
using OrigPeg as the temporary
peg for this transfer *)
DoTowers (NumDiscs-1,
TempPeg, NewPeg, OrigPeg)
end
end;
(*****************************************************)
begin (* Main *)
write ('Please enter the number
of discs in the tower ===> ');
readln (numdiscs);
writeln;
DoTowers (numdiscs, 1, 3, 2)
end. (* Main *)
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