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 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 t
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
someone posted a 200,000 char test-string:
http://pastebin.com/raw.php?i=a8veAND3
(doesn't view properly in chrome, view-source and save)
and the previous code failed pretty hard..
so, new approach
- one pass has all the information on where each character occurs. so,
create a map with each char
i could get it down to around 1.6/1.7 seconds
s...@sid-:~$ time clojure dummy.clj
woohoo palindrome: eve
woohoo palindrome: ranynar
real0m1.739s
user0m2.088s
sys 0m0.124s
made a couple of changes
- only call 'palindrome?' for substrings between identical
characters(between
I think the indexing in all-combs may be off, causing it to miss
certain combinations/substrings.
user=> (all-combs "abc")
("a" "ab")
I used this instead:
(defn substrings [s]
(let [length (count s)]
(for [i (range length)
j (range (inc i) (inc length))]
(subs s i j
us
On Oct 12, 2010, at 3:02 PM, tonyl wrote:
> (defn palindrome? [s]
> (= s (reduce str (reverse s
One opportunity to micro-optimize is to replace "reduce str" with "apply str".
str uses a StringBuilder object to build a string from its arguments. When you
use reduce, the code walks down s a
I'm just replying because I also do this in clojure and my level is
also
really slow:
http://github.com/krsanky/greplin-challenge/blob/master/greplin-challenge/src/greplin_challenge/level1.clj
:)
--paul wisehart
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I new the palindrome? function wasn't good in performance, but I
didn't think it would be that bad. The type hinting does improve
performance plus a mid way to compare.
Thanks for pointing that out and the max-key function.
On Oct 12, 4:15 pm, Justin Kramer wrote:
> The 'palindrome?' function can
The 'palindrome?' function can be made much faster. Your version --
which is idiomatic and fine when perf isn't a factor -- turns the test
string into a sequence, reverses it, turns it back into a string, then
checks for full equality with the original. There are faster (if
uglier) ways to check fo
So for returns a lazy-seq of the combinations and I am forcing it to
process the values by filtering.
mmm...
I still tried your approach and nothing changed in processing time.
I changed the for form to filter as it is pairing the combinations, I
didn't think it would make any difference since I ju
I actually played with this on Saturday morning while waiting for a friend, and
thought it was an interesting problem.
Your example is spending most of its time filtering with palindrome? across all
682695 items generated by all-combs. To see, try:
(defn tony []
(def source "I like racecars t
Hi, I just started to learn clojure in a more serious way and I am
doing the first level of the greplin challenge.
I made it to work with a short palindrome like the example they give
me, but when it comes to work with the input file, it takes for ever
and I have to stop it.
$ time clj level1.clj
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