umm well a string of three characters ( T,C,G,A) , from among these, will be given to the hash function which will generate an index. Can i simply do something like this, if the input is TTT index is 0 , if TCT , index is 1 and so on

Question

umm well a string of three characters ( T,C,G,A) , from among these, will be given to the hash function which will generate an index.   Can i simply do something like this, if the input is TTT index is 0 , if TCT , index is 1 and so on

anonymous · Answer

Okay, you have 4 distinct characters and a hash function. You input a string, of a certain length and only containing only those characters, into this hash function

Now, is the input string of fixed length? Like is it always three characters long?

anonymous · Answer

just take the lexigraphical value of the string (ie.  T-84, C-67,  G-71, A-65) add them all together (if string is "AAA" then 65+65+65) and then modulo (%) that result by the size of your hash table. (if hash table has index size of 10 then result%10) and thats your index

anonymous · Answer

yes, the input string is of fixed length i.e 3 like TGC or TTT etc.

anonymous · Answer

umm can you tell me what is lexigraphical value ? :$

anonymous · Answer

A character's ASCII value: http://en.wikipedia.org/wiki/ASCII#ASCII_printable_characters ChadBro's hash function is sufficient, though not perfect. This is because you can have two inputs that have the same group of characters but in different ordering. In other words, TAG and GAT would collied.

anonymous · Answer

ohh yes this is what i was thinking :) Thanks alot

anonymous · Answer

i don't think there can be a perfect hash function for this problem :S Some collissions would be there :S

anonymous · Answer

can you please help me with this ?? How to make a hash function with minimum number of collissions in this case ? :(