I'm not sure about your requirements. I wrote a solution that produces
This seems more consistent with your stated requirements than your example results. 4 & 8 are equally common -- they appear twice in the arrays. 4 occurs before 8 in $b, thus the elements appear in $b's order of insertion.
At any rate, my algorithm was:
- Traverse all the arrays, counting how many of each element appear.
- Sort the results in order of ascending frequency and assign it to @frequency.
- Take the last of these (i.e. most frequent, or tied for most frequent, and thus common to all) and assign it to $common.
- Die with an error message if $common < the number of arrays -- there wasn't really an element common to all.
- Start building the results for each array:
- First, assign $common.
- Then, for each element in @frequency, test if that element is present in the current array. If it is, assign it to the results for this array. Do this X-1 times (assigning $common took care of one element.)
- Sort this array's results.
- Push an arrayref for this array's results on your final results array.
Updated: my unstated assumption in the above was that that code would be in a subroutine to be called like so:
my ($a_, $b_, $c_) = mutually_exclusive($X, $a, $b, $c);
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