How can I return a combined Int from an [Int] array?

Question

I have an [Int] array like so:

[1, 2, 3]

How can I apply a function on this so it returns:

?

Check this: https://stackoverflow.com/questions/38165569/concatenate-swift-array-of-int-to-create-a-new-int — Kishan Bhatiya, Sep 17 '20 at 10:43

score 1 · Answer 1 · answered Sep 17 '20 at 10:46

1

We can do like below...

var finalStr = ""
    [1,2,3].forEach {
        finalStr.append(String($0))
    }
    if let number = Int(finalStr) {
        print(number)
    }

answered Sep 17 '20 at 10:46

Mahendra

1

This can be simplified using `map`: `let number = Int([1,2,3].map(String.init).joined())` – Dávid Pásztor Sep 17 '20 at 11:10

Bradley Mackey · Accepted Answer · 2020-09-18T11:09:14.733

1

let nums = [1, 2, 3]
let combined = nums.reduce(0) { ($0*10) + $1 }
print(combined)

Caveats

Make sure the Int won't overflow if the number gets too long (+2⁶³ on a 64-bit system).
You need to also be careful all numbers in the list aren't more than 9 (a single base-10 digit), or this arithmetic will fail. Use the String concatenation technique to ensure that all base-10 numbers are correctly handled. But, again, you need to be careful that the number won't overflow if you choose to convert it back to an Int.

edited Sep 18 '20 at 11:09

answered Sep 17 '20 at 10:48

Bradley Mackey

@JoakimDanielson it complicates the example and is a non-issue if only used for small use-cases like OP demonstrates (there are also a variety of possible failure-modes, which depend on OP's use case). – Bradley Mackey Sep 17 '20 at 11:10
Yeah you're correct, it was misleading being at the start. – Bradley Mackey Sep 17 '20 at 11:14
1

This assumes all integers in the collection are from 0 to 9. `[1, 2, 32]` would result in 152 – Leo Dabus Sep 17 '20 at 15:39
@LeoDabus Very true. Answer is edited. – Bradley Mackey Sep 18 '20 at 11:09

2 Answers2