CheckNumbersUsedAreAllInNumbersAllowed

Question 1

Why is a Temp list created to check whether the numbers used are in numbersAllowed?

Answer 1

We don’t want to mutate the actual NumbersAllowed just for checking, so we clone it to Temp.
List<int> Temp = new List<int>();</int></int>

Question 2

How are the numbers used in the RPN expression verified or rejected?

Answer 2

If every numeric token in the RPN expression is found in the temporary list, we remove it.

if (CheckValidNumber(Item, MaxNumber))
if (Temp.Contains(Convert.ToInt32(Item)))
{
Temp.Remove(Convert.ToInt32(Item));
}
// returns true

If we ever fail to find a number, the method returns false.

Question 3

Why is this function used ?

Answer 3

Used in PlayGame to confirm the user’s expression is not using “forbidden” or “unavailable” numbers.