sort a String array in Swift

Question

I have a big array like that :

var tableau = ["Salut", "Hey", "Salut", "Hey", "Hey", "Mom", "Hey", "Dad", "Mom", "Hey", "Plop"]

And now I want an array with each word sort by the number of repeats so an Array like that :

var tableauTrier = ["Hey", "Salut", "Mom", "Dad", "Plop"]

How can I use the least memory to sort them ? Help me please !

vacawama · Accepted Answer · 2017-06-12 15:51:20Z

6

var tableau = ["Salut", "Hey", "Salut", "Hey", "Hey", "Mom", "Hey", "Dad", "Mom", "Hey", "Plop"]

var counts = [String: Int]()

// generate dictionary of counts for each word
for word in tableau {
    counts[word] = (counts[word] ?? 0) + 1
}

// Sort the tuples based on the count and use map to extract the word
let result = counts.sorted { $0.value > $1.value }.map { $0.key }
print(result)

// ["Hey", "Mom", "Salut", "Plop", "Dad"]

edited Jun 12, 2017 at 15:51

answered Jun 12, 2017 at 14:43

vacawama

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2 Comments

Leo Dabus Over a year ago

For better readability since Swift 3 (I think) it can also be written as counts.sorted { $0.value > $1.value }.map { $0.key }

vacawama Over a year ago

I like that @LeoDabus. It makes the solution more obviously correct. A quick check with the IBM Swift Sandbox verifies that this feature did indeed come with Swift 3.0.

vadian · Accepted Answer · 2017-06-12 15:10:36Z

1

Alternatively – just for fun – a solution with NSCountedSet

let tableau = ["Salut", "Hey", "Salut", "Hey", "Hey", "Mom", "Hey", "Dad", "Mom", "Hey", "Plop"]
let set = NSCountedSet(array: tableau)
let array = (set.allObjects as! [String]).sorted(by: {set.count(for: $0) > set.count(for: $1)})
print(array) 
// [Hey, Mom, Salut, Dad, Plop]

edited Jun 12, 2017 at 15:10

answered Jun 12, 2017 at 14:58

vadian

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5 Comments

smcroissant Over a year ago

What a funny solution

vacawama Over a year ago

You'll need to make sure Foundation is imported.

vadian Over a year ago

@vacawama Yes, but in iOS you will import UIKit anyway which includes Foundation

vacawama Over a year ago

You're resulting array is [Any]. If you need [String] you'll want to cast result.

vacawama Over a year ago

True, UIKit includes Foundation, but folks might not import UIKit for a model class.

konrad.bajtyngier · Accepted Answer · 2017-06-12 14:40:37Z

0

With a little helper array, you can got about it like this:

var tableau = ["Salut", "Hey", "Salut", "Hey", "Hey", "Mom", "Hey", "Dad", "Mom", "Hey", "Plop"]
var unique = Array(Set(tableau))
unique.sort { (str1, str2) -> Bool in
    let str1Count = tableau.reduce(0, { (result, str) -> Int in
        return  str == str1 ? result+1 : result
    })
    let str2Count = tableau.reduce(0, { (result, str) -> Int in
        return  str == str2 ? result+1 : result
    })
    return str1Count > str2Count
}

answered Jun 12, 2017 at 14:40

konrad.bajtyngier

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Comments

paulvs · Accepted Answer · 2017-06-12 15:24:35Z

0

Here are a solution:

var result = tableau.sorted(by: { current, next in
    tableau.filter { $0 == current }.count > tableau.filter { $0 == next }.count
}).reduce([String](), {
    if $0.contains($1) {
        return $0
    } else {
        var newPartial = $0
        newPartial.append($1)
        return newPartial
    }
})

print(result)  // ["Hey", "Salut", "Mom", "Dad", "Plop"]

edited Jun 12, 2017 at 15:24

answered Jun 12, 2017 at 15:12

paulvs

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