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Another programming challenge is to compute anagrams from a dictionary and output the longest sets of anagrams first. We submitted the following elegant 3-line F# solution:

let words = System.IO.File.ReadAllLines @"unixdict.txt"
[|for _, words in Seq.groupBy (Array.ofSeq >> Array.sort) words -> Array.ofSeq words|]
|> Array.sortBy (fun s -> -Seq.length s)

This tiny program produces the following sets of anagrams in only half second:

val it : string [] [] =
  [|[|"alger"; "glare"; "lager"; "large"; "regal"|];
    [|"caret"; "carte"; "cater"; "crate"; "trace"|];
    [|"abel"; "able"; "bale"; "bela"; "elba"|];
    [|"elan"; "lane"; "lean"; "lena"; "neal"|];
    [|"angel"; "angle"; "galen"; "glean"; "lange"|];
    [|"evil"; "levi"; "live"; "veil"; "vile"|];
    [|"aden"; "dane"; "dean"; "edna"|]; [|"emit"; "item"; "mite"; "time"|];
    [|"pare"; "pear"; "rape"; "reap"|];
    [|"esprit"; "priest"; "sprite"; "stripe"|];
    [|"hare"; "hear"; "hera"; "rhea"|]; [|"resin"; "rinse"; "risen"; "siren"|];
    [|"keats"; "skate"; "stake"; "steak"|];
    [|"lascar"; "rascal"; "sacral"; "scalar"|];
    [|"amen"; "mane"; "mean"; "name"|]; [|"nepal"; "panel"; "penal"; "plane"|];
    [|"lemon"; "melon"; "menlo"; "monel"|];
    [|"least"; "slate"; "stale"; "steal"|]; [|"leap"; "pale"; "peal"; "plea"|];
    [|"ames"; "mesa"; "same"; "seam"|]; [|"leapt"; "petal"; "plate"; "pleat"|];
    [|"lien"; "line"; "neil"; "nile"|]; [|"abet"; "bate"; "beat"; "beta"|];
    [|"mate"; "meat"; "tame"; "team"|]; [|"beard"; "bread"; "debar"; "debra"|];
    [|"lament"; "mantel"; "mantle"; "mental"|];
    [|"aires"; "aries"; "arise"; "raise"|]; [|"enol"; "leon"; "lone"; "noel"|];
    [|"cereus"; "recuse"; "rescue"; "secure"|];
    [|"manor"; "moran"; "norma"; "roman"|];
    [|"latus"; "sault"; "talus"; "tulsa"|]; [|"diet"; "edit"; "tide"; "tied"|];
    [|"lima"; "mail"; "mali"; "mila"|]; [|"are"; "ear"; "era"; "rae"|];
    [|"apt"; "pat"; "pta"; "tap"|]; [|"dare"; "dear"; "erda"; "read"|];
    [|"ate"; "eat"; "eta"; "tea"|]; [|"ant"; "nat"; "tan"|];
    [|"yates"; "yeast"; "yeats"|]; [|"nerve"; "never"; "verne"|];
    [|"ether"; "there"; "three"|]; [|"dave"; "vade"; "veda"|];
    [|"earn"; "near"; "rena"|]; [|"brag"; "garb"; "grab"|];
    [|"magneto"; "megaton"; "montage"|]; [|"earnest"; "eastern"; "nearest"|];
    [|"den"; "end"; "ned"|]; [|"lair"; "liar"; "rail"|];
    [|"alton"; "talon"; "tonal"|]; [|"now"; "own"; "won"|];
    [|"earth"; "hater"; "heart"|]; [|"dire"; "reid"; "ride"|];
    [|"bard"; "brad"; "drab"|]; [|"bare"; "bear"; "brae"|];
    [|"earthen"; "hearten"; "teheran"|]; [|"kale"; "lake"; "leak"|];
    [|"arnold"; "roland"; "ronald"|]; [|"cpu"; "cup"; "puc"|];
    [|"earthy"; "hearty"; "thayer"|]; [|"abut"; "tabu"; "tuba"|];
    [|"lame"; "male"; "meal"|]; [|"hank"; "kahn"; "khan"|];
    [|"riot"; "tori"; "trio"|]; [|"dater"; "trade"; "tread"|];
    [|"rite"; "tier"; "tire"|]; [|"army"; "mary"; "myra"|];
    [|"alert"; "alter"; "later"|]; [|"acts"; "cast"; "scat"|];
    [|"carven"; "cavern"; "craven"|]; [|"grate"; "great"; "greta"|];
    [|"rosa"; "soar"; "sora"|]; [|"argot"; "gator"; "groat"|];
    [|"demo"; "dome"; "mode"|]; [|"klein"; "kline"; "liken"|];
    [|"lisa"; "sail"; "sial"|]; [|"cruel"; "lucre"; "ulcer"|];
    [|"along"; "anglo"; "logan"|]; [|"listen"; "silent"; "tinsel"|];
    [|"list"; "silt"; "slit"|]; [|"iran"; "nair"; "rain"|];
    [|"baird"; "braid"; "rabid"|]; [|"dearth"; "hatred"; "thread"|];
    [|"ape"; "epa"; "pea"|]; [|"eros"; "rose"; "sore"|];
    [|"ares"; "sear"; "sera"|]; [|"acm"; "cam"; "mac"|];
    [|"gas"; "gsa"; "sag"|]; [|"acme"; "came"; "mace"|];
    [|"part"; "rapt"; "trap"|]; [|"argon"; "groan"; "organ"|];
    [|"ester"; "steer"; "terse"|]; [|"acre"; "care"; "race"|];
    [|"brain"; "brian"; "rabin"|]; [|"parse"; "spare"; "spear"|];
    [|"bin"; "ibn"; "nib"|]; [|"result"; "rustle"; "ulster"|];
    [|"armco"; "macro"; "marco"|]; [|"janos"; "jason"; "jonas"|];
    [|"ante"; "nate"; "neat"|]; [|"goer"; "gore"; "ogre"|]; ...|]

This is one of the shortest and fastest of all the solutions on Rosetta Code. For example, the Haskell solution is more than twice as long at 8 lines of code.

Labels: anagram, rosetta code, sequence expressions, sort, string

# posted by Jon Harrop @ 21:46