Given an unsorted array of integers, Count number of sub arrays in an array having sum k

CountSubArraysProblem.swift

import UIKit
import PlaygroundSupport

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

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