Task «Safe extraction of a value from a chain of optionals»

You are given a string containing integers separated by spaces. Some numbers may be missing (replaced by '?'). Write a function that takes a string, splits it into components, converts each component into an optional Int using Int($0). If the component is '?', it should be converted to nil. Then, from the resulting array of optionals, extract and sum all values that are not nil using a compact optional chain (e.g., via compactMap and reduce). If after processing there are no numbers left, return nil. Otherwise, return the sum as an Int. Input: a single string. Output: an integer or the string "nil".

Example 1

Example 2

Example 3