unique substrings

question.swift

import Cocoa

func fewestCoins(coins: String) -> Int {

  let coinsArray = Array(coins)
  let checkSet :Set = Set(coinsArray)
  let countedSet :NSCountedSet = NSCountedSet()
  // validation when the lenght of the string == amount uniq characters
  if(checkSet.count == coins.count || checkSet.count == 0) {
    return coins.count
  }

  // brute force with sliding window
  var left = 0, right = 0, smallResult = coins.count
  while (right < coinsArray.count || left < coinsArray.count ) {
    if (countedSet.count == checkSet.count) {
      smallResult = min(smallResult, right - left)
      left += 1
      countedSet.remove(coinsArray[left])
    } else if right < coinsArray.count {
      countedSet.add(coinsArray[right])
      right += 1
    } else {
      countedSet.remove(coinsArray[left])
      left += 1
    }
  }

  return Int(smallResult)
}

fewestCoins(coins: "asdfkjeghfalawefhaef")
fewestCoins(coins: "bab")
fewestCoins(coins: "cbbbdcbba")