twoSum Leetcode question 1 with Swift Generics

summedPair

import Foundation

/*
Given an array of integers, return indices of the two numbers such that they add up to a specific target.

You may assume that each input would have exactly one solution, and you may not use the same element twice.

Example:

Given nums = [2, 7, 11, 15], target = 9,

Because nums[0] + nums[1] = 2 + 7 = 9,
return [0, 1].
*/

extension Sequence where Element: AdditiveArithmetic, Element: Hashable {
  func summedPair(_ search: Element) -> (Int,Int)? {
    var compliments = [Element:Int]()
    for (idx, element) in self.enumerated() {
      let comp: Element = search - element
      if let found = compliments[element] {
        return (found, idx)
      } else {
        compliments[comp] = idx
      }
    }
    return nil
  }
}