user: ## Description

You've been working with a lot of different file types recently as your interests have broadened.

But what file types are you using the most? With this question in mind we look at the following problem.

Given a `List/Array` of Filenames (strings) `files` return a `List/Array of string(s)` contatining the most common extension(s). If there is a tie, return a sorted list of all extensions.

### Important Info:

* Don't forget, you've been working with a lot of different file types, so expect some interesting extensions/file names/lengths in the random tests.
* Filenames and extensions will only contain letters (case sensitive), and numbers.
* If a file has multiple extensions (ie: `mysong.mp3.als`) only count the the last extension (`.als` in this case)


## Examples

```
files = ['Lakey - Better days.mp3', 
         'Wheathan - Superlove.wav', 
         'groovy jam.als', 
         '#4 final mixdown.als', 
         'album cover.ps', 
         'good nights.mp3']
```

would return: `['.als', '.mp3']`, as both of the extensions appear two times in files.

```
files = ['Lakey - Better days.mp3', 
         'Fisher - Stop it.mp3', 
         'Fisher - Losing it.mp3', 
         '#4 final mixdown.als', 
         'album cover.ps', 
         'good nights.mp3']
```
would return `['.mp3']`, because it appears more times then any other extension, and no other extension has an equal amount of appearences.

Answer: {"fn_name": "solve", "inputs": [[["direful.pr", "festive.html", "historical.wav", "holistic.mp3", "impossible.jar", "gentle.cpp", "gleaming.xml", "inconclusive.js", "erect.jar", "befitting.mp3", "brief.wp", "beautiful.jar", "energetic.pt", "careful.wp", "defective.cpp", "icky.wav", "gorgeous.txt", "good.pt", "fat.pt", "bored.als", "adaptable.cpp", "fumbling.exe", "grieving.wp", "efficient.wav", "fearful.xml", "damp.html", "erect.exe", "annoyed.xml", "elderly.ala", "far-flung.txt", "careful.mp3", "actually.pt", "cynical.ala", "complex.exe", "extra-small.pt", "enchanted.ala", "amazing.html", "bashful.h", "hallowed.html", "entertaining.html", "bad.js", "illegal.maya", "deadpan.html", "furtive.wp", "hanging.css", "drunk.py", "capricious.wav", "damaging.Ue4", "cool.Ue4", "ambitious.css", "fortunate.wp", "electric.mp3", "crowded.txt", "cooperative.html", "graceful.pt", "aboard.pt", "exclusive.als", "glossy.css", "fluffy.pt", "cluttered.txt", "halting.cpp", "glib.cpp", "aback.pr", "cynical.Ue4", "chilly.xml", "hideous.ala", "finicky.txt", "feigned.ala", "better.Ue4", "dear.py", "available.xml", "easy.pr", "fine.mp3", "cowardly.jar", "incredible.css", "adhesive.exe", "energetic.mp3", "harmonious.exe", "general.als", "condemned.als", "flawless.als", "curvy.h", "ambitious.mp3", "disillusioned.xml", "bitter.h", "hanging.wp", "certain.cpp", "flashy.html", "cuddly.pr", "cagey.Ue4", "extra-small.pr", "amuck.cpp", "direful.html", "delightful.als", "helpless.h", "foamy.mp3", "enthusiastic.maya", "good.maya", "adhesive.css", "imperfect.pr", "bent.cpp", "exultant.zbrush", "adorable.mp3", "clammy.maya", "gaudy.pt", "blushing.css", "cuddly.Ue4", "curved.py", "boring.html", "broken.txt", "daily.jar", "giddy.xml", "curved.css", "future.maya", "graceful.css", "guiltless.maya", "gentle.cpp", "few.css", "calculating.txt", "clear.pr", "grey.py", "entertaining.ala", "elfin.txt", "excited.js", "abject.zbrush", "best.js", "boundless.wav", "hurried.ala", "delirious.cpp"]], [["dramatic.txt", "incompetent.jar", "alcoholic.wp", "clumsy.py", "abject.h", "boring.exe", "aloof.pr", "familiar.py", "fanatical.py", "ill-informed.html", "fierce.pr", "accurate.html", "grotesque.pr", "brown.py", "courageous.pt", "grouchy.jar", "giant.pt", "dirty.h", "abaft.jar", "enormous.zbrush", "creepy.cpp", "beneficial.py", "absorbing.ala", "heartbreaking.html", "exclusive.js", "fluttering.html", "happy.als", "fresh.pr", "adamant.txt", "awful.maya", "frightening.maya", "bizarre.html", "efficacious.exe", "illegal.wav", "dizzy.js", "gusty.wp", "delightful.pt", "full.als", "chivalrous.xml", "filthy.js", "functional.jar", "conscious.wav", "feeble.exe", "hilarious.cpp", "earthy.py", "handy.txt", "hollow.cpp", "aggressive.js", "fat.h", "drunk.exe", "clear.h", "easy.wav", "eatable.pt", "grumpy.css", "empty.exe", "brief.jar", "aggressive.txt", "aggressive.txt", "gruesome.ala", "awake.txt", "apathetic.mp3", "holistic.pt", "embarrassed.css", "flashy.maya", "exultant.ala", "exuberant.exe", "graceful.pt", "dependent.py", "gigantic.wp", "husky.js", "immense.pr", "defiant.cpp", "cooperative.html", "frantic.maya", "abashed.css", "dysfunctional.h", "gusty.js", "dynamic.txt", "dreary.pt", "giddy.ala", "exciting.css", "best.als", "humdrum.css", "busy.jar", "frail.cpp", "cagey.wav"]], [["freezing.jar", "frail.xml", "available.txt", "excited.als", "godly.exe", "fair.zbrush", "abortive.Ue4", "ill-fated.mp3", "early.cpp", "demonic.py", "greedy.css", "high.py", "dry.xml", "fascinated.html", "humorous.zbrush", "hilarious.pr", "burly.pt", "cumbersome.wp", "elite.Ue4", "equable.py", "cold.h", "discreet.wp", "hard.mp3", "aberrant.css", "common.zbrush", "fretful.maya", "erect.js", "good.maya", "general.wav", "complete.js", "ad hoc.jar", "healthy.mp3", "bawdy.exe", "impartial.py", "hesitant.pt", "erratic.css", "agonizing.cpp", "belligerent.html", "cumbersome.Ue4", "chilly.h", "bustling.exe", "curly.jar", "gorgeous.py", "friendly.txt", "discreet.html", "abhorrent.ala", "awake.Ue4", "good.Ue4", "closed.html", "gabby.py", "imminent.js", "combative.css", "feigned.ala", "elderly.ala", "glamorous.h", "dry.xml", "illustrious.html", "first.xml", "conscious.xml", "divergent.zbrush", "doubtful.xml", "big.ala", "brief.h", "clever.als", "fierce.ala", "adventurous.html", "ashamed.jar", "fast.cpp", "fanatical.py", "ambiguous.pr", "efficient.txt", "gullible.jar", "ill-informed.cpp", "capable.py", "aboard.mp3", "complete.als", "helpful.maya", "bizarre.css", "filthy.js", "hateful.Ue4", "aback.wp", "fertile.html", "cloudy.als", "comfortable.css", "bustling.js", "ad hoc.py", "adorable.ala", "frequent.als", "flimsy.mp3", "aboriginal.pt", "blushing.h", "feigned.py", "bloody.py", "hospitable.ala", "extra-large.cpp", "alike.exe", "fine.js", "confused.wav", "bloody.wp", "cumbersome.wav", "harsh.mp3", "crooked.css", "equal.wav", "drunk.als", "general.cpp", "grieving.css", "certain.cpp", "cumbersome.pt", "different.txt", "flat.h", "cagey.h", "enormous.wp", "difficult.xml", "furry.pt", "enormous.exe", "dramatic.h", "brief.zbrush", "elfin.zbrush", "cumbersome.pt"]], [["fresh.exe", "groovy.pr", "debonair.pr", "hesitant.Ue4", "curious.py", "black.als", "elderly.zbrush", "harmonious.wav", "different.cpp", "ablaze.xml", "abstracted.html", "hollow.zbrush", "familiar.xml", "defiant.mp3", "huge.exe", "efficacious.html", "aberrant.ala", "better.js", "glamorous.wp", "glossy.cpp", "gentle.jar", "incandescent.exe", "bashful.js", "aware.pr", "hellish.js", "icky.cpp", "chivalrous.pr", "exotic.xml", "grandiose.js", "abrupt.html", "bitter.mp3", "chemical.xml", "disagreeable.exe", "far-flung.exe", "acrid.wp", "infamous.Ue4", "hungry.xml", "deadpan.h", "equable.wp", "hanging.txt", "fanatical.Ue4", "excellent.Ue4", "grieving.js", "brash.css", "gullible.pr", "acid.py", "fragile.html", "bewildered.jar", "bored.zbrush", "illustrious.zbrush", "equal.cpp", "female.wp", "coordinated.cpp", "elderly.txt"]], [["hanging.h", "fixed.ala", "first.pr", "cooperative.cpp", "elfin.zbrush", "fair.pr", "cool.css", "highfalutin.py", "alcoholic.maya", "heady.cpp", "befitting.wav", "certain.jar", "glistening.exe", "attractive.wav", "gruesome.wp", "happy.txt", "finicky.jar", "clumsy.js", "assorted.js", "highfalutin.cpp", "damaging.h", "ethereal.xml", "great.jar", "dead.wp", "acoustic.xml", "devilish.css", "curly.pt", "exuberant.ala", "flippant.wp", "holistic.html", "cut.txt", "adamant.py", "dashing.zbrush", "conscious.wp", "black-and-white.cpp", "elated.pt", "high-pitched.exe", "flowery.xml", "glib.wp", "industrious.html", "arrogant.zbrush", "accessible.html", "classy.jar", "acceptable.maya", "cynical.pt", "erratic.pt", "earthy.als", "dramatic.als", "bite-sized.py", "ahead.xml", "giddy.js", "fortunate.txt", "early.txt", "imaginary.wav", "cute.zbrush", "graceful.html", "far-flung.Ue4", "goofy.exe", "abundant.mp3", "ambitious.txt", "gigantic.jar", "abashed.xml", "guiltless.Ue4", "adventurous.py", "guarded.jar", "extra-large.zbrush", "filthy.h", "easy.zbrush", "glorious.als", "detailed.pr", "flashy.zbrush", "breezy.als", "faithful.py", "curly.js", "chief.js", "concerned.js", "cumbersome.zbrush", "ahead.maya", "berserk.cpp", "deserted.pt", "cool.zbrush", "broken.cpp", "glossy.pt", "deep.xml", "average.wav", "dangerous.cpp", "acrid.wav", "dear.zbrush", "deeply.pr", "detailed.cpp", "friendly.h", "first.css", "heady.exe", "far-flung.als", "erratic.mp3", "exciting.pr"]], [["crazy.pr", "black-and-white.als", "illegal.wav", "exultant.mp3", "exotic.jar", "capricious.pt", "abundant.ala", "eatable.zbrush", "careful.py", "godly.css", "clever.txt", "dusty.maya", "awesome.zbrush", "discreet.jar", "creepy.h", "fair.pt", "descriptive.mp3", "boundless.ala", "berserk.xml", "hungry.exe", "awful.exe"]], [["cLgvr.P.als", "sgeFl.FL.als", "j9Yei.Kyu.py", "RljRS.v.ala", "1CJaz.EJF.pr", "Zxc1b.tOw.maya", "s0lXz.P7z.txt", "QvISi.b8l.Ue4", "3XtjW.rSSH.zbrush", "6TsCH.dJy.zbrush", "ZbL5a.zeqk.ala", "1RReC.Pk3.zbrush", "0EfHO.Ic.pr", "VGBzm.o.h", "BJZtt.6.xml", "xU84j.0MC.pt", "l3JMW.RMg.py", "kAbbu.8Il.ala", "G0ecb.BnPc.jar", "dwll1.tpL.wav", "CQMue.p55.js", "98tu7.Zcp.ala", "gutGx.Hel.cpp", "utRUl.B5c.ala", "qjOwJ.Z7K5.h", "ltygD.Q8b.jar", "8eH8W.5J1.py", "cu6hY.Ux.zbrush", "vrFaN.jLZ.pr", "7dZyA.NOKB.mp3", "h5i96.Xa3u.maya", "q7zW3.Am0o.pr", "1i0rP.qhl.pr", "Lnb3P.vW8B.html", "dEa97.zU.maya", "nYfS1.eLB.ala", "B48eD.m8i.html", "UiF8F.lME.maya", "y65gi.Hy.xml", "dstKJ.Jw2.Ue4", "WPPqa.TG6.als", "kespD.XwYz.ala", "MGdVy.jOH.py", "4kIBi.UES.py", "gWeqd.KY.pt", "KmFlM.XbG.h", "V6cPb.WnX.mp3", "Dh0Qi.75t.maya", "VIIGI.yI.jar", "5xXJB.1b.cpp", "H0eqG.9w.h", "lqf3u.AC.txt", "6p9Wy.p.html", "vpocy.2SJ.wp", "Buf8Y.zIL.wp", "MqT4y.4Ht.css", "PdB3m.KF.ala", "fExGF.gOU.ala", "VrCoD.JK.cpp", "QJFt9.ODPT.wav", "NGWzW.l.py", "IepDH.tjU.txt", "ldVGH.qehX.wav", "F6trP.yqC.mp3", "J5O28.XeHt.zbrush", "91FXj.uA.ala", "mf7Ah.8mG.maya", "hv11B.a1e.jar", "voQGw.NPPT.h", "hUtNN.0Dpu.txt", "44Yzo.2v6T.txt", "zVkzf.W2.exe", "ea1Fh.uCL.mp3", "gnla7.s.cpp", "7H1YL.SNp.maya", "xoh3J.N.js", 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"gz7rb.aI.wav"]], [[]]], "outputs": [[[".cpp", ".html"]], [[".pt", ".py", ".txt"]], [[".py"]], [[".cpp", ".exe", ".js", ".pr", ".xml"]], [[".zbrush"]], [[".ala", ".exe", ".jar", ".mp3", ".pt", ".zbrush"]], [[".ala"]], [[]]]}