Question

I was asked this interview question. I am not sure what the correct answer for it is (and the reasoning behind the answer):

Is sin(x) a good hash function?

Answer 1

If you mean sin(), it’s not a good hashing function because:

• it’s quite predictable and for some x it’s no better than just x itself. There should be no seemingly apparent relationship between the key and the hash of the key.
• it does not produce an integer value. You cannot index/subscript arrays with floating-point indices and there must be some kind of array in the hash table.
• floating-point is very implementation-specific and even if you make a hash function out of sin(), it may not work with a different compiler or on a different kind of CPU/computer.
• sin() may be much slower than some simpler integer-arithmetic function.