On Fri, Jul 23, 2010 at 1:26 PM, Emil Chacko <emilcha...@gmail.com> wrote:
> Below given is solution to a puzzle( > http://projecteuler.net/index.php?section=problems&id=14) in python and c > > Python: > > import time > startT=time.time() > maxlen=0 > longest=0 > for i in xrange(1,1000000): > last=i > cnt=0 > while(last <> 1): > cnt=cnt+1 > if(last%2==0): > last=last/2 > else: > last=3*last+1 > if(cnt>maxlen): > maxlen=cnt > longest=i > print "time taken (sec) : ",time.time()-startT > print maxlen,longest > > Python Output: > time taken (sec) : 99.4702298641 > 524 837799 > > C: > > #include <stdio.h> > int main(int argc, char **argv) > { > int longest = 0; > int maxlen = 0; > int i; > unsigned long last; > for (i = 1; i <= 1000000; i++) > { > last = i; > int cnt = 0; > while (last != 1) > { > cnt++; > if (last % 2 == 0) > last = last / 2; > else > last = 3 * last + 1; > } > if (cnt > maxlen) > { > maxlen = cnt; > longest = i; > } > } > printf("longest: %d (%d)\n", longest, maxlen); > return 0; > } > > > My doubt is that in C the result comes in 1-2 sec but in python it takes 99 > secs.I don't expect python to be as fast as c but i cant understand why it > should be so slow in python.i'm new to python so if there is better way to > do the above prog in python please suggest. > Your python code as is clocked about 72 seconds on my notebook. The following came in at about 4.6 seconds (just has a small trick of reusing earlier results) import time start =time.time() longest = None longest_elements = 0 solved = {} for val in xrange(1,1000000) : counter = 1 number = val while number != 1 : number = number / 2 if number % 2 == 0 else 3 * number + 1 if number in solved : counter = counter + solved[number] break else : counter = counter + 1 if counter > longest_elements : longest_elements = counter longest = val solved[val] = counter end = time.time() print "Time:", end - start print longest, ':', longest_elements Dhananjay > _______________________________________________ > BangPypers mailing list > BangPypers@python.org > http://mail.python.org/mailman/listinfo/bangpypers > -- -------------------------------------------------------- blog: http://blog.dhananjaynene.com twitter: http://twitter.com/dnene _______________________________________________ BangPypers mailing list BangPypers@python.org http://mail.python.org/mailman/listinfo/bangpypers
