I'm using ELF Hash to write a specially tweaked version of hash map. Wanting to produce collisions

问题

Can any one give an example of 2 strings, consisting of alphabetical characters only, that will produce the same hash value with ELFHash?

I need these to test my codes. But it doesn't seem like easy to produce. And to my surprise there there are a lot of example codes of various hash function on the internet but none of them provides examples of collided strings.

Below is the ELF Hash, in case you need it.

unsigned int ELFHash(const std::string& str)
{
   unsigned int hash = 0;
   unsigned int x    = 0;

   for(std::size_t i = 0; i < str.length(); i++)
   {
      hash = (hash << 4) + str[i];
      if((x = hash & 0xF0000000L) != 0)
      {
         hash ^= (x >> 24);
         hash &= ~x;
      }
   }

   return (hash & 0x7FFFFFFF);
}

回答1:

You can find collisions using a brute force method (e.g. compute all possible strings with length lower than 5).

Some example of collisions (that I got in that way):

hash = 23114:
-------------
UMz
SpJ

hash = 4543841:
---------------
AAAAQ
AAABA

hash = 5301994:
---------------
KYQYZ
KYQZJ
KYRIZ
KYRJJ
KZAYZ

来源：https://stackoverflow.com/questions/5920276/im-using-elf-hash-to-write-a-specially-tweaked-version-of-hash-map-wanting-to