Swift: Terminated by Signal 4 - swift

Question

I'm trying to write a function that has arrayOne, arrayTwo, and arrayThree as inputs. If arrayTwo has any 0s as its last elements, the function is supposed to remove these elements from the array, as well as the same elements from arrayOne. When I run the code and try to test it, I get the error: "Terminated by signal 4".
What could the problem be?
var arrayOneNew = arrayOne
var arrayTwoNew = arrayTwo
var arrayThreeNew = arrayThree
var endElement = arrayTwoNew.last
if endElement == 0 {
var counter = arrayTwoNew.count
while arrayTwoNew[counter] == 0 {
var elementToBeRemoved = arrayTwoNew.remove(at: counter - 1)
var 2ndElementToBeRemoved = arrayOneNew.remove(at: counter - 1)
}
}

Answer 1

Your main problem is that you are setting counter to arrayTwoNew.count which is 1 bigger than the last valid index in arrayTwoNew, so while arrayTwoNew[counter] == 0 crashes with index out of range.
Also:
var elementToBeRemoved = arrayTwoNew.remove(at: counter - 1)
is probably meant to remove the last item from arrayTwoNew, but that is more easily accomplished with:
arrayTwoNew.removeLast()
especially since you're not using elementToBeRemoved.
I think you're trying to do this:
while arrayTwoNew.last == 0 {
arrayTwoNew.removeLast()
arrayOneNew.removeLast()
arrayThreeNew.removeLast()
}

Answer 2

You are creating a new array "arrayTwoNew" which is mixed up with the original one at
var arrayTwoNew = arrayTwoNew.remove(at: counter - 1)
Now I'm also struggling with your .remove - this returns an element so won't work. I'd usually use a filter here but I'm not sure what you are doing!
//code with remove taken out (replace with filter?) to get you started:
let arrayOne = [1,2,3]
let arrayTwo = [2,3,4]
let arrayThree = [5,6,7]
var arrayOneNew = arrayOne
var arrayTwoNew = arrayTwo
var arrayThreeNew = arrayThree
var endIndex = arrayTwoNew.last
if endIndex == 0 {
let counter = arrayTwoNew.count
// arrayTwoNew = arrayTwoNew.remove(at: counter - 1)
while arrayTwoNew[counter] == 0 {
// arrayOneNew = arrayOneNew.remove(at: counter - 1)
}
}