Try using a modified class, rather than a function.

Nevermind my post, I thought there was something missing about the backtracking, but I checked again, and found that it is indeed clear what is meant!

Yep, thank you :)
It didn't occur to me to print stuff on Codewars.. : P
Thanks for being friendly telling a newcomer a really basic thing.

He gets lost between 5 and 6, I think going back to 4 might be the problem.

Need some help clarifying this kata.

In the case of this riders([21, 35, 28, 18, 13, 23, 45], 6), here's my reasoning:

1. Rider 1 starts from Station 1 and gets to Station 4. (21 + 35 + 28 = 84)
2. Rider 2 starts from Station 4 and wanders off somewhere between Station 5 and Station 6. (> 18)
3. Rider 3 from Station 6 starts looking for Rider 2 and found him somewhere between Station 5 and Staiton 6, and then escorts Rider 2 back to Station 4. (18 + 13 = 31)
4. Rider 3 starts from Station 4 and gets as far as Station 7. ((31) + 18 + 13 + 23 = 85)
5. Rider 4 starts from Station 7 and gets to the end. (45)

So we need 4 riders in total. But the test case says 3. What did I get wrong?

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@myjinxin - You are a man of few words :-)

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Kata which are nothing more than recipes where every nuance is spelled out are boring. If all you have to do is code exactly a pre-described algorithm, then where's the fun in that?

I prefer to write Kata which appear easy at first, but may contain subtle "gotchas". They teach you to think before you code. They teach you to be more patient - to avoid leaping to conclusions and going off half-cocked. They re-enforce RTFM lessons. But mostly it just makes finding the solution much more satisfying.

on the contrary, it's perfectly in adequation with the provided information... ;)

nope, you're wrong. Rider 3 cannot get to S6.

Please check expected value for ([33,8,16,47,30,30,46],5). Your code expects 5, while it looks to me that the correct answer is 4.
Here is the screenshot of expected. http://rgho.st/6HgTK5QG4
And here is a picture (like the one in your example) that proves 4.http://rgho.st/private/65nspjs9c/59f62919b9838551cd0aba66bf51a646