@zLuki 2 substractions and 2 divisions? what if the sequence is consistent at the start but not in the middle? What if it the sequence breaks at the end of the sequence? They won't be a valid AP/GP anymore. Thus, you have to loop through the entire list to check. 2 check is not enough

LOL

Will do it.

sure

[0, 1, 0, 1, 0] --> 0 # none

Maybe -1?

Enforced 1 liner solutions will give this a 5, otherwise a 8 :)

Can you please make this a 6kyu one. Because I haven't seen any question as hard as this in 7kyu's.

I thought it was a 6kyu one. But the person approved it put it as 7kyu I guess. I cant do anything.

Too difficult to be a 7kyu.

No more issues, so we can approve?

Looks good :)

Fixed

[189, 0, 0, 0, 0]
-1 should equal 0

[681, 0, 0, 0, 0]
-1 should equal 0

[511, 0, 0, 0, 0]
-1 should equal 0

[188, 0, 0, 0, 0]
-1 should equal 0

[27, 0, 0, 0, 0]
-1 should equal 0

The tests are wrong again.

Are you just changing stuff at random hoping that this time it will be correct?

Done!!

It is correct. You can go and read any article on AP and GP.

No it is not. The Wikipedia article on arithmeric progressions doesn't list any limitations for a_1 or d, and googling for "arithmetic progression zero difference" gives results stating that a_1 = d = 0 is valid.

Also, it is amusing to hear this from a person who expected a list of zeros to be classified as a geometric progression when, according to Wikipedia (at least), it isn't actually one.

I am no math guy and the only source I used is Wikipedia, but from what I;ve read there:

• in a definition of an arithmetic progression, difference d is not constrained in any way and can be 0.
• in a definition of a geometric progression, ratio r is defined to be different than 0.

If these rules are correct, it would mean that:

• [42, 0] is a valid arithmetic progression with d=-42. It's not a valid geometric progression, because r would be 0
• [42, 0, 0] is not a valid arithmetic progression, and it's not a valid geometric progression because r would be 0
• [0, 0, 0] is a valid arithmetic progression with d=0. I am not sure if it's a valid geometric progression or not, because r can be anything, be it 0 or not. I think it's not a GP, I am not sure though.
• [42, 42, 42] is a valid arithmetic progression with d=0. It's also a valid geometric progression with a ratio of 1
• [-42, 42, -42, 42] would not be an arithmetic progression, but a valid geometric progression with r=-1

So basically cases with [x, 0, ...more zeros...] are nasty edge cases, because:

• when x is 0, it's AP but not a GP (examples: [0, 0], [0, 0, 0]). It's also different than [x ,x, x] because for x != 0 it's both AP and GP (example: [42, 42, 42])
• when x is not 0, things depend on its length
  • when length is 2, it's AP but not GP (example: [42, 0])
  • when length is more than 2, it's neither AP nor GP (example: [42, 0, 0])

Things depend on defintion, and maybe there are other definitions than ones I found on Wikipedia. But cases with trailing zeros are really tricky because answer depends on what's the first term, and what's the length of the progression.