CODEWITHSUNDEEP
arraysswiftmultidimensional-array
Ahmad F
Ahmad F

Reputation: 31645

How to find the summation of all elements in 2d array in Swift?

Let's say that I have the following 2d array:

let my2dArray = [[01, 02, 03, 04],
                 [05, 06, 07, 08],
                 [09, 10, 11, 12],
                 [13, 14, 15, 16]]

What is the easiest way to get the summation of all elements in my2dArray?

Assuming that the output should be:

01 + 02 + 03 + 04 + 05 + 06 + 07 + 08 + 09 + 10 + 11 + 12 + 13 + 14 + 15 + 16 = 136

Upvotes: 3

Views: 1642

Answers (3)

Ahmad F
Ahmad F

Reputation: 31645

I came up with:

Non-Swifty Solution (Works as it should, but not "Swifty"):

var summation = 0

for i in 0..<my2dArray.count {
    for j in 0..<my2dArray[i].count {
        summation += my2dArray[i][j]
    }
}

print(summation) // 136

Swifty Solution (The easiest way):

let summation = my2dArray.map { $0.reduce(0, +) }.reduce(0, +)

print(summation) // 136

Any other -more efficient- "Swifty" solution would be really appreciated.

Upvotes: 1

vacawama
vacawama

Reputation: 154603

One way is to use joined() to flatten the array and then reduce to sum it:

let my2dArray = [[01, 02, 03, 04],
                 [05, 06, 07, 08],
                 [09, 10, 11, 12],
                 [13, 14, 15, 16]]

let result = my2dArray.joined().reduce(0, +)

print(result) // 136

Note that my2dArray.joined() doesn't create another array, but instead it creates a FlattenBidirectionalCollection<Array<Array<Int>>> which allows sequential access to the items, both forwards and backwards, but it does not allocate new storage. You can of course do Array(my2dArray.joined()) if you wish to see how it looks in array format.

Upvotes: 6

twiz_
twiz_

Reputation: 1198

Just a couple more ways to do this:

let my2darray = [[01, 02, 03, 04],
             [05, 06, 07, 08],
             [09, 10, 11, 12],
             [13, 14, 15, 16]]



let doubleReduced = my2darray.reduce(0, {$1.reduce(0, +) + $0})
let dontForgetFlatmap = my2darray.flatMap{$0}.reduce(0,+)

Upvotes: 3

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