Given an unsorted array of integers, find a subarray which adds to a given number

SubArrayCountProblemIncludingNegative.swift

import UIKit
import PlaygroundSupport

func findSubArrayWhoseCountMatches(targetValue: Int, in array: [Int]) -> [Int] {
  var sum = 0
  var hashMap = [Int: Int]()
  
  for index in 0..<array.count {
    sum = sum + array[index]
    if sum == target {
      return [0, index]
    }
    if let valueIndex = hashMap[sum - targetValue] {
      let startIndex = valueIndex + 1
      return [startIndex, index]
    }
    hashMap[sum] = index
  }
  return []
}

let arr = [10, 2, -2, -20, 10]
let target = 0
let subArrayIndexes = findSubArrayWhoseCountMatches(targetValue: target, in: arr)
print(subArrayIndexes)