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Unique hash function for every tweet in Twitter?

+1 vote
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This was asked today in interview any pointer.

"Design a unique hash function for every tweet in Twitter"

posted Oct 4, 2015 by anonymous

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The unique hash function or unique index mapped from the key (twitter tweets )?
Finding the unique hash function ? I don't think so if yes please let me know.
I think it should be simple i.e. finding the hash function for the "string in tweet + user_handle" (two people can have same tweet but should have different index). Then we need to handle the exceptions i.e. retweet etc.

1 Answer

+1 vote

What you need is hash function which takes input as string and userhandle (original person who tweeted the matter). Rest is simple (handle the collision in the hash) -

Modified sdbm

static unsigned long sdbm(unsigned char *tweet, unsigned char *handle)
{   
    unsigned long hash = 0;
    int c;
    while (c = *tweet++)
            hash = c + (hash << 6) + (hash << 16) - hash;

    while (c=*handle++)
            hash = c + (hash << 6) + (hash << 16) - hash;

    return hash;
}
answer Oct 5, 2015 by Salil Agrawal
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+1 vote

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 H(string1 . string2) = H(string1) op H(string2)

 where:
 H() is the hash function    
 string1 is a string
 string2 is a string    
 . is the string concatenation operator 
 f() is a function
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