Add Two Numbers

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].

Solution

class TwoSum {
  func twoSum(_ nums: [Int], _ target: Int) -> [Int] {
    var dict = [Int: Int]()
    for (index, value) in nums.enumerated() {
      dict[value] = index
    }
    for (currentIndex, value) in nums.enumerated() {
      if let index = dict[target - value], index != currentIndex {
        return [currentIndex, index]
      }
    }
    return []
  }
}