The Swift Programming Language Book Chapter Section on Control Flow Experiment 3

Like this:

let interstingNumbers = [
"Prime": [2, 3, 5, 7, 11, 13, 17],
"Fibonacci": [1, 1, 2, 3, 5, 8],
"Square": [1, 4, 9, 16, 25, 36],
]
var largest = 0
var largestKind = ""
for (kind, numbers) in interstingNumbers {
    for number in numbers {
        if number > largest {
            largest = number
            largestKind = kind
        }
    }
}
largest
largestKind