CODEWITHSUNDEEP
iosswift
user8977455
user8977455

Reputation:

Multiply and add elements in 2 arrays

I have 2 arrays say arrayA & arrayB. arrayA has the elements say [1,2] and arrayB has the elements say [3,4]. Now I want to multiply and add the elements in these arrays like so.. 1x3 + 2x4 = 11. How can I achieve this...?

Upvotes: 1

Views: 1447

Answers (3)

mugx
mugx

Reputation: 10105

Here a combo of zip, map and reduce:

let result = (zip([1,2], [3,4]).map { $0.0 * $0.1 }).reduce(0, +)
print(result) // 11
  1. Zip makes a sequence of pairs based on the two arrays: (1,3), (2,4)
  2. with map I am iterating for each element of the array producing at each iteration a new element
  3. $0 means the element of the sequence at the current iteration. Since the element is a pair (because of zip), we can access to the first sub-element of the pair with $0.0 and to the second with $0.1.
  4. finally (after map) we get an array of products, just need to "reduce" it to a number, summing all the resulting elements with reduce.
  5. (0, +) means that reduce starts from 0 as initial value, then with the abbreviation + we can accumulate the sums of all the elements.

Upvotes: 9

dfrib
dfrib

Reputation: 73176

Note that rather than using a chained map and reduce (for multiplication and summation, respectively), you could directly apply the reduce operation on the zipped sequence, and modify the reduce closure to accordingly calculate the sum of the pair-wise multiplied objects in the zipped sequence:

let a = [1, 2]
let b = [3, 4]

let result = zip(a,b).reduce(0) { $0 + $1.0 * $1.1 } // 11

Upvotes: 2

Md. Mostafizur Rahman
Md. Mostafizur Rahman

Reputation: 481

Try this.

let A = [1,2]
let B = [3,4]

let C = zip(A, B).map {$0.0 * $0.1}

print(C) // [3, 8]

let sum = C.reduce(0, +)

print(sum)//11

Upvotes: 0

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