Question

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...?

Answer 1

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

Zip makes a sequence of pairs based on the two arrays: (1,3), (2,4)
with map I am iterating for each element of the array producing at each iteration a new element
$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.
finally (after map) we get an array of products, just need to "reduce" it to a number, summing all the resulting elements with reduce.
(0, +) means that reduce starts from 0 as initial value, then with the abbreviation + we can accumulate the sums of all the elements.

Answer 2

请注意，您可以直接对压缩序列应用REL操作，而不是使用链式map和reduce（分别用于乘法和求和），并修改{ {1}}闭包以相应地计算压缩序列中成对乘法对象的总和：

reduce

Answer 3

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

Multiply and add elements in 2 arrays

3 个答案: