Find an algorithm (subroutine) that when called repeatedly with the same character-string variable that is initialized with n characters, all different, will cycle through all the permutations of those n characters, so that for example, when called 24 times with a string of length 4, will have cycled that string through all 24 permutations and returned it to its initial state.

Here's a solution which requires a separate tracking array:

 

AllPermutations(DataArray(), TrackingArray())( 

	/* Written by Erik Oosterwal */

	i=0 

	While(TrackingArray(i)== i+1)( 
		i++ 
		) 

	Mirror(DataArray(0), i+2) 

	for(j=0, j<i+1, j++)(
		TrackingArray(j-1)=0 
		) 

	TrackingArray(i)++ 
	return(DataArray(), TrackingArray())
	) 

Posted by Erik on 2004-06-02 09:10:10