TheGameCreators - CodeBase - Recursive Functions: The Towers of Hanoi

Category: Complete Applications

Version: 1.1

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Uploaded: 24th Jun 2007 21:29

Modified: 25th Jun 2007 22:40

Author: Libervurto

Summary

The Towers of Hanoi Problem: the computer completes the puzzle using an example of recursive function calling. [EDIT] The program will now set itself a new challenge each time it completes the puzzle!

Full Description

The classic puzzle where you have 3 ever decreasing rings and 3 poles, the aim being to move all three rings from the left poles to the far right by only moving one ring at a time and only placing a ring on an empty pole or larger ring.<br /> I got the pseudo code for this out of a book, it was pretty difficult transferring it to BASIC and working out how to display it. I still don't quite understand the implementations for recursive functions, though as you can see they are extremely clever and economic.

DarkBASIC Source Code

` This code was downloaded from The Game Creators

` It is reproduced here with full permission

` http://www.thegamecreators.com

`*** The Towers of Hanoi Problem ***

`I will use binary system to store rings on poles (1=small ring, 2=medium, 4=large)

DIM Pole(3)

source = 1 : `set start pole

`setup

hide mouse

sync on

`set up new puzzle

repeat : destination= rnd(2)+1 : until destination <> source : `get end pole

repeat : temporary_store= rnd(2)+1 : until temporary_store <> source and temporary_store <> destination

Pole(source) = 7 : Pole(destination) = 0 : Pole(temporary_store) = 0 : `initiate poles

display() : `display the initial puzzle

print "New destination: " ; destination : sync : wait 1000 : `begin puzzle message

source = Transfer(3, source, destination, temporary_store) : `complete the puzzle and return new source

LOOP

`Transfer

FUNCTION Transfer(N, source, destination, temporary_store)

`Problem Fix Variables

S = source

D = destination

T = temporary_store

If N = 1

Move(S, D)

Else

Transfer(N-1, S, T, D)

Move(S, D)

Transfer(N-1, T, D, S)

Endif

ENDFUNCTION destination

`Move

FUNCTION Move(source, destination)

`which ring is to be moved?

Select Pole(source)

Case 1 : ring = 1 : Endcase

Case 2 : ring = 2 : Endcase

Case 3 : ring = 1 : Endcase

Case 4 : ring = 4 : Endcase

Case 5 : ring = 1 : Endcase

Case 6 : ring = 2 : Endcase

Case 7 : ring = 1 : Endcase

Endselect

`Take ring from source and add to destination

Pole(source) = Pole(source) - ring

Pole(destination) = Pole(destination) + ring

`Update display

Display()

ENDFUNCTION

`Display

FUNCTION Display()

cls

For x = 1 to 3

`draw poles

ink rgb(120,40,0),0

Line 100+(100*x), 100, 100+(100*x), 200

`disintegrate pole variables

ink rgb(255,200,0),0

pole = Pole(x) : `store current pole rings value

rings = 0

`big ring?

if pole - 4 >=0

inc rings

box 100+(100*x)-40, 183-((rings-1)*20), 100+(100*x)+40, 200-((rings-1)*20)

pole = pole - 4

endif

`medium ring?

if pole - 2 >=0

inc rings

box 100+(100*x)-30, 183-((rings-1)*20), 100+(100*x)+30, 200-((rings-1)*20)

pole = pole - 2

endif

`small ring?

if pole - 1 >=0

inc rings

box 100+(100*x)-20, 183-((rings-1)*20), 100+(100*x)+20, 200-((rings-1)*20)

pole = pole - 1

endif

Next x

sync

wait 1000

ENDFUNCTION

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Author Name:	Libervurto
CodeBase Entries:	11

CodeBase - Recursive Functions: The Towers of Hanoi

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