Swift Challenge

Everything is optional!

Congratulations on finding another Hummus Challenge. In this challenge, we've hidden the next clue in some randomized data about people and their hummus creations. A common problem with data, though, is that sometimes people leave things blank! Even with missing data, we still need to be able to sort it.
Sort the data and decode the clue!

Below is a sample dataset that has already been sorted. Notice how it is sorted in increasing order by each column. If two rows have the same value in a column, then they are sorted by the next column. Also notice that in a correct sort for this challenge, nil values are considered the smallest.

Finally, to get the clue you'll need to decode each "Rating" integer as its corresponding ASCII character. Once you have the data sorted, the first 18 rows that have non-nil Ratings will be your clue!

Response:

Your Decoding:

To solve this challenge, you must submit a Swift file with a function that sorts the rows of data and decodes the clue. The data is given in the form of a 2D array. Looking at the sample data, each row of the table corresponds to a single array. Your goal is to sort the arrays, not the data within those arrays.

Don't have Swift on your computer? Debug your code on REPL.it

Requirements

Submit a Swift file with a function named “sortAndDecode”
func sortAndDecode(_ arr: [[Any?]]) -> (String, [[Any?]])
Function Parameter:
- arr: A 2D array of optional values of Any type
Return: A tuple with the following 2 items in the following order
- String: The Clue, decoded from decimal (integer) ASCII values
- [[Any?]]: The sorted array of arrays

Sorting in Swift

The easiest way to sort in Swift is with the built in sorting functions, either sort(by: ) or sorted(by: ). These functions take a function or closure as the argument. The function you pass in will allow the sorter to decide if one element should go before the other. If it returns true, the first argument should come before the second. Consider the basic example of passing in the less than operator, which operates the same way.

let arr = [3,2,1] arr.sort(by: <) // arr is now [1,2,3]

But we aren't sorting integers, we're sorting arrays of optional "Any" type objects. You'll need something more complex than <. Read on for more tips.

Swift Optionals

In Swift, optional values can either have a value or be "nil". To use the value in an optional, you should use optional binding.

However, our data is in arrays of optional "Any" types, and "Any" objects cannot be compared. Strings and integers are comparable, so we need to convert the object back to its original type.

In your sort function when you compare two rows, you'll have to access the string or integer for comparison. Optional binding and attempting to convert to a type looks like this.
if let stringVal = optionalAnyVal as? String { // Code }

Because Swift is statically typed, you need to know the type at compile time. For this challenge, as you can see in the sample data, all arrays have 5 string elements and 1 integer element in that order. One possible solution: Anytime you want to compare elements from indices 0-4, you should try to optionally bind to a string. If you have to compare by the element at index 5, optionally bind to an integer.

One final hint. Consider your comparison function passed in to the sort(by: ) function. It takes in two [Any?] arrays. It should compare them "column by column". For one comparison you have 4 cases.

item1	item2	Result
nil	nil	Compare the next column
nil	Not nil	return true
Not nil	nil	return false
Not nil	Not nil	return valueOfItem1 < valueOfItem2

Good Luck!