Without { }, the loop will operate on the following statement instead of the following code block. If the loop had a semicolon on the end, then it would be truly pointless. Try the following code:

Code:

int n;
for(n=0; n<10; n++)
  printf("loop A %d\n", n);

for(n=0; n<10; n++);
  printf("loop B %d\n", n);

It looks to me like the intent was to only work on the following line -- why strip the value to table size every loop instead of just once -- so code blocks were left out. Better indenting would have showed the intent. For maximum clarity they could've surrounded the single line.

---------- Post updated at 09:34 AM ---------- Previous update was at 09:10 AM ----------

As for improving the hash function, there's not a lot to it as is. Slowdowns may be coming from other things. How full are your hash tables, how many collisions are you getting?