Custom string sorting in Swift

Question

I have an array that I want sorted alphabetically (for the most part). For example I want an array of string to be sorted A-Z with the exception of elements starting with "g", I want elements starting with "g" to be last (or first if that's easier) in the array.

Example:

let list = ["apple", "car", "boat", "zebra", "ghost", "far"]

sorted should be:

["apple", "boat", "car", "far", "zebra", "ghost"]

How would one accomplish this?

jnpdx · Accepted Answer · 2021-06-09 03:18:32Z

1

You could use sorted(by:) and compare cases that start with "g" and then fallback to normal String comparison if that doesn't happen:

let sorted = list.sorted { a, b in
    if a.first == "g" && b.first != "g" { return false }
    if b.first == "g" && a.first != "g" { return true }
    return a < b
}

answered Jun 9, 2021 at 3:18

jnpdx

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1 Comment

Sweeper Over a year ago

I think a single expression such as (!$0.hasPrefix("g") && $1.hasPrefix("g")) || (!$0.hasPrefix("g") && $0 < $1) works too, right?

aheze · Accepted Answer · 2021-06-09 03:18:54Z

0

I would split it into 2 arrays, sort each of them, then combine them again.

let list = ["apple", "car", "boat", "zebra", "ghost", "far"]
let listWithoutG = list.filter { !$0.hasPrefix("g") }
let listOnlyG = list.filter { $0.hasPrefix("g") }

let sorted = listWithoutG.sorted() + listOnlyG.sorted()
print("Sorted: \(sorted)")

Result:

Sorted: ["apple", "boat", "car", "far", "zebra", "ghost"]

answered Jun 9, 2021 at 3:18

aheze

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