Two Sum
1 min read

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

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