very nice! faster and more succinct :) also means we can read in smaller chunks from large strings as required..
On Oct 21, 4:15 am, Kent <squi...@aol.com> wrote: > I took a different approach, not wildly "clojurish", type-hinted, > ugly, but also pretty fast. About 1.2ms on my machine (after about 10 > runs so the JIT has done its magic). > > The approach is to look at each character, or pair of adjacent > characters, as the potential center of a palindrome and then "grow" > the palindrome out from that seed until it looses its palindromness. > > Kent. > > (def st > "Fourscoreandsevenyearsagoourfaathersbroughtforthonthiscontainentanewnation > conceivedinzLibertyanddedicatedtothepropositionthatallmenarecreatedequalNow > weareengagedinagreahtcivilwartestingwhetherthatnaptionoranynartionsoconceiv > edandsodedicatedcanlongendureWeareqmetonagreatbattlefiemldoftzhatwarWehavec > ometodedicpateaportionofthatfieldasafinalrestingplaceforthosewhoheregavethe > irlivesthatthatnationmightliveItisaltogetherfangandproperthatweshoulddothis > Butinalargersensewecannotdedicatewecannotconsecratewecannothallowthisground > Thebravelmenlivinganddeadwhostruggledherehaveconsecrateditfaraboveourpoorpo > nwertoaddordetractTgheworldadswfilllittlenotlenorlongrememberwhatwesayhereb > utitcanneverforgetwhattheydidhereItisforusthelivingrathertobededicatedheret > otheulnfinishedworkwhichtheywhofoughtherehavethusfarsonoblyadvancedItisrath > erforustobeherededicatedtothegreattdafskremainingbeforeusthatfromthesehonor > eddeadwetakeincreaseddevotiontothatcauseforwhichtheygavethelastpfullmeasure > ofdevotionthatweherehighlyresolvethatthesedeadshallnothavediedinvainthatthi > snationunsderGodshallhaveanewbirthoffreedomandthatgovernmentofthepeoplebyth > epeopleforthepeopleshallnotperishfromtheearth") > > (defn longest-palindrome-at [^String st ind1 ind2] > > (let [ind1 (int ind1) > ind2 (int ind2)] > (if (= (.charAt st ind1) > (.charAt st ind2)) > (if (or (zero? ind1) (= ind2 (dec (.length st)))) > [ind1 ind2] > (recur st (dec ind1) (inc ind2))) > [(inc ind1) (dec ind2)]))) > > (defn longest [^String st] > (let [[ind1 ind2] > (apply max-key (fn [[i1 i2]] (let [i1 (int i1) i2 (int i2)] > (- i2 i1))) > (concat > (for [i (range (.length st))] > (longest-palindrome-at st i i)) > (for [i (range 1 (.length st))] > (longest-palindrome-at st (dec i) i))))] > (.substring st ind1 (inc ind2)))) -- You received this message because you are subscribed to the Google Groups "Clojure" group. To post to this group, send email to clojure@googlegroups.com Note that posts from new members are moderated - please be patient with your first post. To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en
