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Challenging Programming Exercises Published Weekly

programmingpraxis.com

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Re: Challenging Programming Exercises Published Weekly

#3

Post by gryphonic »

For more math oriented challenges (more project euler like), check out the monthly IBM 'I ponder this'. These are usually quite challenging, but the problems are interesting and solutions are posted at the end of the month. http://domino.research.ibm.com/Comm/wwwr_ponder.nsf/pages/in...

Re: Challenging Programming Exercises Published Weekly

#4

Post by jschulenklopper »

Obligatory link to a nice and long-running initiative: Project Euler: http://projecteuler.net/.

"Project Euler is a series of challenging mathematical/computer programming problems that will require more than just mathematical insights to solve. Although mathematics will help you arrive at elegant and efficient methods, the use of a computer and programming skills will be required to solve most problems."

Re: Challenging Programming Exercises Published Weekly

#7

Post by eddington »

Complete solution to today's problem in one line of python

def gen(univ, n=5): return univ if n == 1 else [x+y for y in gen(univ,n-1) for x in univ if all([(x+y)[start:start+upto] != (x+y)[start+upto:start+upto*2] for start in range(len(x+y)) for upto in range(1,(len(x+y)-start+2)/2)])]

... god that looks ugly. Call it with

>>> gen(["1", "2", "3"], 5) ['13121', '23121', '21321', '31321', '12321', '12131', '32131', '21231', '31231', '13231', '13212', '23212', '21312', '12312', '32312', '12132', '32132', '23132', '21232', '31232', '31213', '13213', '23213', '12313', '32313', '32123', '13123', '23123', '21323', '31323']

Re: Challenging Programming Exercises Published Weekly

#9

Post by peteretep »

eddington wrote: post #7

Complete solution to today's problem in one line of python def gen(univ, n=5): return univ if n == 1 else [x+y for y in gen(univ,n-1) for x in univ if all([(x+y)[start:start+upto] != (x+y)[start+upto:start+upto*2] for start in range(len(x+y)) for upto in range(1,(len(x+y)-start+2)/2)])] ... god that looks ugly. Call it with >>> gen(["1", "2", "3"], 5) ['13121', '23121', '21321', '31321', '12321', '12131', '32131', '2…

And in some rather nicer Perl:

    sub solutions {
    	my ( $target_length, $alphabet, $head ) = @_;
    	$head //= '';    

    	# Base Case our head is the right length
    	return $head if (length $head) == $target_length;

    	# General Case
    	return
    		map  { generate( $target_length, $alphabet, $_ ) }    
    		grep { ! /(.{2})\1/ }
    		map  { $head . $_ }
    		@$alphabet;
    }
eg:

    my @solutions = solutions( 5, [1..3] );

Re: Challenging Programming Exercises Published Weekly

#10

Post by JasonFruit »

peteretep wrote: post #9
eddington wrote: post #7

Complete solution to today's problem in one line of python def gen(univ, n=5): return univ if n == 1 else [x+y for y in gen(univ,n-1) for x in univ if all([(x+y)[start:start+upto] != (x+y)[start+upto:start+upto*2] for start in range(len(x+y)) for upto in range(1,(len(x+y)-start+2)/2)])] ... god that looks ugly. Call it with >>> gen(["1", "2", "3"], 5) ['13121', '23121', '21321', '31321', '12321', '12131', '32131', '2…

And in some rather nicer Perl: sub solutions { my ( $target_length, $alphabet, $head ) = @_; $head //= ''; # Base Case our head is the right length return $head if (length $head) == $target_length; # General Case return map { generate( $target_length, $alphabet, $_ ) } grep { ! /(.{2})\1/ } map { $head . $_ } @$alphabet; } eg: my @solutions = solutions( 5, [1..3] );

That's quite pretty Perl. You've lessened my prejudice against the language by writing code that can be read.
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