Check if all the values are not null. Remember, that string can be nullable

This is a bummer, I am having the same issue. It looks like it is the first test case, but we can't see it.

I have the same error with C#
Did you get an answer to this?

Hello,
myjinxin2015, maybe you have any thoughts about my question or you see any mistakes?
Thanks

There is no difference between "in dictionary order" and "alphabetic order", I think ;-)
About the code, I can't give you more help, unless you give more information about fails, or paste your code below(Mark as having spoiler content)

Changed < to <=, Thanks for your feedback ;-)

The part of the description that says "unique letters (2 < length <= 26)" should be changed to "unique letters (2 <= length <= 26)" because the random tests include strings with 2 letters. This was a really cool kata that forced me to learn more about permutations, though, thanks!

I have the same issue.

Hi,
I run my code and one of the tests (not a sample test) get me an error:
"MyTest
System.NullReferenceException : Object reference not set to an instance of an object"
And without any additional description of the error I have no idea where it's failed and which test case uses. I'm using C# and VS.