I agree with Phani.. however there the hash function that is used must have some mathematical properties.. lets assume u have a hash function H such that
Key ----> H -----> Value .. then Value -----> H' ------> Key where H' is the inverse function of H. Hence your original hash function must be a single valued, monotonically increasing function so that you have an inverse function H' which uniquely maps your values back to the keys.. On Mar 27, 12:53 am, "Debajit Adhikary" <[EMAIL PROTECTED]> wrote: > Could you clarify this please? > > On Wed, Mar 26, 2008 at 11:39 PM, phani bandaru <[EMAIL PROTECTED]> > wrote: > > > > > Given value you can easily find the key using hash function it self.- > > Find2(v) > > If we just have one hash table, that is enough to do the first two > > operations. Insert & Find1 > > > On 3/27/08, Sticker <[EMAIL PROTECTED]> wrote: > > > > I was interviewed a question about implementing a bi-direction > > > hashtable, i.e. a hashtable that stores key-value pairs such that you > > > can find value based on key as well as find key based on value. > > > > In another word, there is no obvious difference between a key and a > > > value, your hashtable should have the following functions: > > > 1. Insert(v1, v2); //Insert v1-v2 pair. > > > 2. Find1(v); //Find v2 based on v1. Should take O(1) time. > > > 3. Find2(v); //Find v1 based on v2. Should take O(1) time. > > > > My answer at that time was using two hashtables underlying, one treats > > > v1 as key and v2 as value and the other treats v2 as key and v1 as > > > value. > > > > In this way, some redundant information is kept. For example, by > > > removing v1-v2 pair, we need to remove v1 from on hashtable and v2 > > > from the other. > > > > I wonder whether there is alternate way that store v1-v2 pair as a > > > whole and meanwhile allows quick search based on both v1 and v2. > > > > Many thanks. > > > > -- > > > pUrNamadah pUrNamidam > > > pUrNAt pUrNamudachyate > > > pUrNasya pUrNamAdAya > > > pUrNamevAvashiShyate- Hide quoted text - > > - Show quoted text - --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Algorithm Geeks" group. To post to this group, send email to algogeeks@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/algogeeks -~----------~----~----~----~------~----~------~--~---
