in the ASCII table you will find '\0' is equal to the demical '0'.
*buffer = 0; is equivalent to *buffer = '\0'

But then where in buffer will the char be put? Either buffer must be increased, or you need an index variable.

Edit: oh wait, you're saying in addition to.

I never said it didn't. But I also stated the truth.

Please read this: https://github.com/codewars/codewars.com/wiki/Troubleshooting-your-solution . Also if you want someone to help you out you should post your code here and mark it as having spoiler content.

@Jackyjk yes, 6141381611 is the correct answer for the random test inputs in the OP

I don't really see how that's possible. Is this for JS? Try submitting again.

mine : 6141381611
???

expected NaN to equal NaN
I don't know
wtf? what happened

Your solution does not even pass sample tests. You can start with debugging these locally.

1. Check on what inputs your solution fails (see here how)
2. Recreate failing test case locally, run your solution in your IDE for such input
3. Check if your solution returns correct answer in your IDE. If not, debug through it.