How to generate random number without repetition?

Originally Posted by memcpy

Also note that the error might be because every time you run calloc() in the loop, you're allocating 12,000 bytes. Run this 1500 times, and you'll be allocating 18,000,000 bytes. Your OS probably doesn't allow a single program to take up this much memory.

Oh, it will. But unfortunately the fun doesn't stop at just 1500 times...

Originally Posted by Suntang

allocated row 11597

SUNTANG! THINK! Why is that happening? How many rows did you code that loop to allocate?

Code:

for(r=0; columns; r++)

Either this is a typo you still haven't spotted, or there is something about for() loops you have misunderstood. Either way, there is a major major problem right there. Read posts #23 and #26 carefullly again. In #23, I thought that was not the "real code" but it turned out that it was, which is why I said in #26 "so you do have an infinite loop in there". I thought that would be obvious enough...sorry.