Unique hash function for every tweet in Twitter?

Question

This was asked today in interview any pointer.

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

Comments

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.

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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.

Answer 1

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;
}