Changing the order of an array to be the same as another array SWIFT

Question

I've seen this has been done before but can't seem to find it in swift. So I have two arrays, arrayA and arrayB. I want arrayB to sort itself into the same order a arrayA. So for example her is the arrays:

var arrayA = [1,2,3,4,5]
var arrayB = [4,5,1,2,3]

Thanks

• cmashinho: You want to sort with increase and with decrease?
• Aaron Rasmussen: If you want them to be the same, why not just copy? arrayA = arrayB?
• Martin R: Your question is still unclear to me, but this might be what you are looking for: stackoverflow.com/questions/29432656/….
• Martin R: @HenryBrown: If they have the same elements then you can simply assign arrayB = arrayA.
• matt: This question takes the prize as the most unclear or unnecessary ever asked on Stack Overflow.

Answer 1

1) This is what I understand

arrayA defines some kind of order. In your example it is coincidentally the ascending order of integers but it can really be any kind of order like one of the following:

1. Example 1: [5, 4, 1, 3, 2] Ascending by number "names" (five, four, one, three, two)
2. Example 2: [5, 2, 4, 3, 1]: Ascending by italian names of numbers (cinque, due, quattro, tre, uno)

2) You don't like this kind of solution

arrayB = arrayA

You actually need a way to move the elements inside arrayB in order to make it sorted as arrayA (maybe because you need a solution for a more generic problem where the elements of the arrays are not simply integers).

3) Now, my solution

var arrayA = [1, 2, 3, 4, 5]
var arrayB = [4, 5, 1, 2, 3]
var indexes = [Int: Int]()
for (index, elm) in enumerate(arrayA) {
 indexes[elm] = index
}
// now indexes[i] gives me the position of the integer i inside arrayA, e.g. indexes[3] -> 2
arrayB.sort { return indexes[0ドル] < indexes[1ドル] }
// now arrayB has been sorted as arrayA

Conclusion

This approach does work when:

1. there are not duplicates in arrayA (or arrayB)
2. arrayA.count == arrayB.count
3. arrayA and arrayB contain the same elements

Please let me know if this is what you are looking for.

• Henry Brown: Yes! Perfect! Thank you exactly what I wanted!

Answer 2

I think you just need to use the reverse() function.

var arrayA = [1,2,3,4,5]
arrayB = reverse(arrayA)

will result in arrayB = [5,4,3,2,1] and vice versa.