SortTwisted37.swift

let replacements = [("3", "*"), ("7", "3"), ("*", "7")]
func twisted37(_ val: Int) -> Int {
    return Int(replacements.reduce(String(val), { $0.replacingOccurrences(of: $1.0, with: $1.1) })) ?? 0
}

func sortTwisted37(_ arr: [Int]) -> [Int] {
    return arr.sorted(by: { twisted37($0) < twisted37($1) })
}

assert(sortTwisted37([1,2,3,4,5,6,7,8,9]) == [1, 2, 7, 4, 5, 6, 3, 8, 9])
assert(sortTwisted37([12,13,14]) == [12,14,13])
assert(sortTwisted37([9,2,4,7,3]) == [2, 7, 4, 3, 9])