How to count the individual elements in an array?

Question

I want to count the individual elements in the following array:

let b = [
    1, 2, 3,
    [4,5,6],
    [
        [7,8],
        [9,0]
    ]
]

, and I was able to count the following array:

let a = [
    [1,2,3],
    [4,5],
    [6,7,8,9]
]

with the following code:

protocol DeepCountable {
    var deepCount: Int {get}
}

// conditional conformance
extension Array: DeepCountable where Element: DeepCountable {
    var deepCount: Int {
        return self.reduce(0){$0 + $1.deepCount}
    }
}

extension Int: DeepCountable {
    var deepCount: Int { return 1 }
}

print(a.deepCount)      // 9

How do I do the same thing to array b?

print( b.deepCount )

This might help. https://stackoverflow.com/questions/47544675/flatten-any-array-swift — Rakesha Shastri, Apr 10 '19 at 06:34

RajeshKumar R · Answer 1 · 2019-04-10T11:55:09.243

2

Type of array b is [Any]. Any isn't DeepCountable. Now add a deepcount property in Array

extension Array: DeepCountable {
    var deepCount: Int {
        return self.compactMap({ $0 as? DeepCountable }).reduce(0, { $0 + $1.deepCount })
    }
}

let a = [[1,2,3],[4,5],[6,7,8,9]]
print(a.deepCount)//9
let b = [1, 2, 3,[4,5,6],[[7,8],[9,0]]] as [Any]
print(b.deepCount)//10
let c = [1,2,"a","b"] as [Any]
print(c.deepCount)//2

edited Apr 10 '19 at 11:55

answered Apr 10 '19 at 06:28

RajeshKumar R

15,445
2
38
70

Is this Swift 4 or 5, I can't get it to work in my playground? – Joakim Danielson Apr 10 '19 at 06:44
@JoakimDanielson Swift 4.2 – RajeshKumar R Apr 10 '19 at 06:44
1

Thanks, I was wondering why I couldn't get it to work but it seems to be because I'm on 5.0 then. I like your solution though. – Joakim Danielson Apr 10 '19 at 06:55
FYI, your code doesn't work for the following array: `let d = [1,2,3,[4,5],[6,7,8,[9, 0]]] as [Any]`, which contains an element of type [Any] which is unfortunately not DeepCountable, hence it failed to count the numbers in `[6,7,8,[9,0]]`. – lochiwei Apr 10 '19 at 11:44
@lochiwei Didn't think abt that – RajeshKumar R Apr 10 '19 at 11:55

Joakim Danielson · Answer 2 · 2019-04-10T11:41:49.800

1

Here is a generic solution that can count different types

extension Array {
    func countType<T>(_ elemType: T.Type) -> Int {
        var count = 0
        for elem in self {            
            if let _ = elem as? T {
                count += 1
            } else if let arr = elem as? [Any] {
                count += arr.countType(elemType)
            }
        }
        return count
    }
}

Usage

let b = [1, 2, 3,[4,5,6],[[7,8],[9,0]]] as [Any]
let c = [1,2,"a","b"] as [Any]

print("Int Count    \(b.countType(Int.self))")
print("Array Count  \(b.countType([Int].self))")
print("Int Count    \(c.countType(Int.self))")
print("String Count \(c.countType(String.self))")
print("Array Count  \(c.countType([Int].self))")

yields

Int Count    10  
Array Count  3  
Int Count    2  
String Count 2  
Array Count  0

edited Apr 10 '19 at 11:41

answered Apr 10 '19 at 07:36

Joakim Danielson

43,251
5
22
52

I think RajeshKumar R's solution will work in Swift 5, if you keep my original "conditional conformance" for Array alongside RajeshKumar R's Array extension. – lochiwei Apr 10 '19 at 08:50
@lochiwei No I can't get it to work in my playground – Joakim Danielson Apr 10 '19 at 09:23
@JoakimDanmielson Please see the solution provided by me below, I think it should work. – lochiwei Apr 10 '19 at 11:37
1

@lochiwei Yes that solution works fine for me too. I'll remove my implementation of a computed property from my answer but I'll keep the generic function since I think it has a value here. – Joakim Danielson Apr 10 '19 at 11:41
Can you make your `countType()` to work for any Sequence, not just arrays? – lochiwei Apr 10 '19 at 12:34
@lochiwei I gave it a go but I was not successful, maybe I'll be able to try some more tomorrow. – Joakim Danielson Apr 10 '19 at 14:05

score 0 · Answer 3 · answered Apr 10 '19 at 06:16

0

Firstly you need to flatten the array into single then count that array.

let b = [
    1, 2, 3,
    [4,5,6],
    [
        [7,8],
        [9,0]
    ]
]
let flatb = b.flatMap({ $0 })
print(flatb.count)

answered Apr 10 '19 at 06:16

Zeeshan Ahmed

834
8
13

Did you check this before posting? – Rakesha Shastri Apr 10 '19 at 06:20

score 0 · Answer 4 · answered Apr 10 '19 at 11:33

The following code is the result I concluded from the above contributions:

protocol DeepCountable {
  var deepCount: Int { get }
}

// now any Array is DeepCountable
extension Array: DeepCountable {
  var deepCount: Int {
    return compactMap{ $0 as? DeepCountable }.reduce(0){ $0 + $1.deepCount }
  }
}

extension Int: DeepCountable {
  var deepCount: Int { return 1 }
}

// test
let a = [[1,2,3],[4,5],[6,7,8,9]]
let b = [1, 2, 3,[4,5,6],[[7,8],[9,0]]] as [Any]
let c = [1,2,"a","b"] as [Any]
let d = [1,2,3,[4,5],[6,7,8,[9, 0]]] as [Any]

print( a.deepCount )  //  9
print( b.deepCount )  // 10
print( c.deepCount )  //  2
print( d.deepCount )  // 10

This code should work with Swift 5, I've tried it on Online Swfit Playground, and it works fine.

Instead of using a computed property you should use a throwable function if you want to throw error for invalid arrays like [1,2,"a","b"] — RajeshKumar R, Apr 10 '19 at 11:54

How to count the individual elements in an array?

4 Answers4