Two Sum

Given an array of integers, return whether or not two numbers sum to a given target k.
Note: you may not sum a number with itself.

Ex: Given the following...

[1, 3, 8, 2], k = 10, return true (8 + 2)
[3, 9, 13, 7], k = 8, return false
[4, 2, 6, 5, 2], k = 4, return true (2 + 2)

 fun twoSum(nums: IntArray, target: Int): Boolean {
    val map = HashMap<Int, Int>()
    nums.forEachIndexed { index, item ->
        val found = map[target - item]
        found?.let {
            return true
        }
        map[item] = index
    }
    return false
}

Steps

• Create a new HashMap
• Iterate over the array
  • Subtract current array element from target
  • Check if the above difference exists in HashMap
    • If YES, then return true
    • If NO, then store the current element as HashMap key and current index as its value
• Return false if nums array iteration is completed in the above step