I did but this description sucks

Fair. I could try to receive a dynamic list, check its size, and just then try to cast to a string list.

But the directions say n being the length of the string array, if n = 0 return "", so because the list is empty, you should return an empty string, right?

Also, notice that almost 400 coders have solved it in Dart so far.

Anyway, I don't know Dart, so not sure what else to check.

Althought if you're talking about the 3rd sample test, I was able to pass that one.

Won't work in Dart due to a test passing a empty dynamic list as parameter, when the code itself expects a list of strings:

type 'List' is not a subtype of type 'List' in type cast

i fully forget soo sorry ty!

wkppvixoyxzzzzzzzzzzzz.length = 22

Your solution skipped 3452, going directly for zzzzzzzzzzzz. You shouldn't be able to do that considering it should be consecutive strings.

From the array, the possibilities are:

["it", "wkppv", "ixoyx", "3452", "zzzzzzzzzzzz"]
 ___________1__________
       _____________2__________
                _______________3_______________

1. "it", "wkppv", "ixoyx" (length 12)
2. "wkppv", "ixoyx", "3452" (length 14)
3. "ixoyx", "3452", "zzzzzzzzzzzz" (length 21)

Therefore, the answer is "ixoyx3452zzzzzzzzzzzz".

Not a kata issue.

Incorrect answer for:
strarr=["it", "wkppv", "ixoyx", "3452", "zzzzzzzzzzzz"]
k=3
: expected 'wkppvixoyxzzzzzzzzzzzz' to equal 'ixoyx3452zzzzzzzzzzzz'
?

XD