"We received the following error when we ran your code:" but no error is following

[bakaiadam]

"We received the following error when we ran your code:" but no error is following

[siebenschlaefer]

I don't know why the website reported an error but didn't show it.

But maybe I can help with the code. Look at the constructor. In the function body it assigns num = num;. That doesn't work, officially it reads an uninitialized member variable num (invoking undefined behavior), but in practice that statement will probably do nothing, and num still has an "indeterminate value".
Instead initialize num in the "member initializer list", just like elems: : elems(num), num{num} { } In that context the first num in num{num} refers to the member variable, the second one to the parameter.

[bakaiadam]

thank you. with your help, i managed to solve the exercise.