Not getting max element of array

Question

I have a string array called prodIDArr having values like so...

["1","2","3","4","5","6","7","8","9","10"]

But when I do something like so..

let maxVal = prodIDArr.max()

I get the value of maxVal as 9 and not 10.

What could be the reason for this...?

Strings are compared lexicographically: "1" < "10" < "2" < ... < "9" — Martin R, May 11 '18 at 07:53
It's the order that elements (for example words) would appear in a lexicon https://en.wikipedia.org/wiki/Lexicographical_order — David Rönnqvist, May 11 '18 at 07:59
`xicographically` is alphabetic order in alphabetic string start with 1 less than string start with 9 — Abdelahad Darwish, May 11 '18 at 07:59

Martin R · Accepted Answer · 2018-05-11T08:08:18.913

That is an array of strings, and those are compared lexicographically:

"1" < "10" < "2" < ... < "9"

For example "10" < "2" because the initial characters already satisfy "1" < "2". (For the gory details, see for example What does it mean that string and character comparisons in Swift are not locale-sensitive?.)

Using an array of integers would be the best solution:

let prodIDArr = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
let maxId = prodIDArr.max()
print(maxId) // Optional(10)

If that is not possible then you can enforce a numeric comparison with

let prodIDArr = ["1","2","3","4","5","6","7","8","9","10"]
let maxId = prodIDArr.max(by: { $0.compare($1, options: .numeric) == .orderedAscending })
print(maxId) // Optional("10")

score 0 · Answer 2 · answered May 11 '18 at 09:47

0

You can also map your original String Array to an Int Array

let prodIDArr = ["1","2","3","4","5","6","7","8","9","10"]
let prodNumArray = prodIDArr.map { input in Int(input)!} // or { Int($0)! }
print(prodNumArray.max()!)

answered May 11 '18 at 09:47

claude31

874
6
8

Not getting max element of array

2 Answers2