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Re^2: Puzzle Timeby Athanasius (Canon) 
on Dec 23, 2012 at 10:21 UTC ( #1010086=note: print w/ replies, xml )  Need Help?? 
++LanX for an excellent answer (way faster than my brute force approach). Allow me one nitpick: 9! = 362880 possible combinations are checked in a recursive function. Throwing in a counter shows that sub append_digit is actually called 986,410 times. Took me a while to work out why... 9! is the number of combinations if every number has exactly 9 digits. But we also allow numbers with 1, 2, ..., 8 digits. So the total number of combinations is:
(That 1 extra sub call is the first one, when @number is empty.) :) For anyone else trying to understand how this code works, here is my slightlyreworked version which outputs the results in the order found:
Hope that’s helpful!
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