Sum

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 1:

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

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

Example 2:

Given nums = [3,2,4], target = 6,
Expected:
[1,2]

Example 3: 

Given nums = [3,3], target = 6
Expected:
[0,1]

func sum(_ nums: [Int], _ target: Int) -> [Int] {
    
        
    }