you can calculate nCr using a dynamic programming type algo as nCr = n-1Cr + n-1Cr-1. calculate for largest possible n once .. and once thats done, getting this value would be O(1). Calculating factorial of 500 looks scary
On 23 May 2010 13:49, Mikhail Dektyarev <[email protected]>wrote: > As I know, dict uses trees, not hashes. > And to find the right size is not difficult. 501x501 will be enough, > filling with 0 by default. > > > On Sun, May 23, 2010 at 12:17 PM, Atanas Banov <[email protected]> wrote: > >> errr, no. hash lookup is O(1), not log... you are thinking balanced trees >> or some such. >> also while 2D array will be a bit faster, you will have to deal with >> proper sizing and filling default value. >> >> >> On Sat, May 22, 2010 at 8:18 PM, Terence <[email protected]> wrote: >> >>> Another point is to use array (2-D list) instead of dict to implement >>> cache. this will reduce the time complexity of cache lookup operation from >>> O(logN) to O(1) >>> >>> >> -- >> You received this message because you are subscribed to the Google Groups >> "google-codejam" group. >> To post to this group, send email to [email protected]. >> To unsubscribe from this group, send email to >> [email protected]<google-code%[email protected]> >> . >> For more options, visit this group at >> http://groups.google.com/group/google-code?hl=en. >> > > > > -- > Best regards, Дектярев Михаил > > -- > You received this message because you are subscribed to the Google Groups > "google-codejam" group. > To post to this group, send email to [email protected]. > To unsubscribe from this group, send email to > [email protected]<google-code%[email protected]> > . > For more options, visit this group at > http://groups.google.com/group/google-code?hl=en. > -- You received this message because you are subscribed to the Google Groups "google-codejam" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/google-code?hl=en.
