in the C=3, N=2 case: f(3) = f(1) + 1;//when you are miss 3 card, you will get 2 new cards when you buy a package; f(1) = 1/3*f(1) + 2/3*f(0) + 1;//when you are missing one card, the propobility that you will not get a new card is 1/3. So, f(0)=0; f(1)=1.5; f(3) = 2.5;
On Sat, Sep 12, 2009 at 6:33 PM, Roshan Amadoru <[email protected]>wrote: > > can you show how to get the answer when C=3, N=2.. i'm still a little > confused to be honest. > > bas wrote: > > Let f(k) be the expected number of packs we need to buy if we still > > don't have k cards (or we have C-k cards). > > To solve the problem we need to find f(C). Note: f(0)=0. > > > > In the first example C=2; > > When we buy the first pack, we will get one of the cards we need with > > the probability 1. > > f(2)=1*f(1)+1 > > means that we expect to buy that many packs to get all the cards we > > need. But we still don't know f(1). > > For k=1 we have one card we need, and we need to find the other one. > > When we buy this next pack, we will get the card we already have with > > a probability 1/2 and the card we need with prob 1/2. > > f(1)=1/2*f(1)+1/2*f(0)+1 > > Then: f(1)=2; f(2)=3 > > > > > > > > > > > > On Sep 11, 9:54 pm, qasim zeeshan <[email protected]> wrote: > > > >> Hi All, > >> First of all congrats to all who made it to next round. > >> > >> I have seen some codes for Problem C. but didn't understand. Can anyone > >> please explain both example test cases for Problem C. > >> > >> Thanks > >> > >> -- > >> Qasim Zeeshan > >> > > > > > > > > > > > -- 有D --~--~---------~--~----~------------~-------~--~----~ 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 -~----------~----~----~----~------~----~------~--~---
