// MARK: - TWO SUMM

func twoSum(_ nums: [Int], _ target: Int) -> [Int] {
    var dict = [Int:Int]()
    for (index, num) in nums.enumerated() {
        let dif = target - num

        if dict[dif] != nil {
            return [dict[dif]!, index]
        }

        if dict[dif] == nil {
            dict[num] = index
        }
    }
    return []
}

//twoSum([2,7,11,15], 9)