Inventory Update Problem in Swift

Hey guys, Leo here.

Today we’ll continue the series Algorithms, the Final Frontier. Always remember folks, this is ONE of many possible solutions for the problem. The challenge is here: The Challenge

Let’s go!

The problem: Compare and update the inventory stored in a 2D array against a second 2D array of a fresh delivery. E.G. update inventory([[21, “Bowling Ball”], [2, “Dirty Sock”], [1, “Hair Pin”], [5, “Microphone”]], [[2, “Hair Pin”], [3, “Half-Eaten Apple”], [67, “Bowling Ball”], [7, “Toothpaste”]]) should return an array with a length of 6. Solution: I divide this problem into two parts:

  1. Create a compiled inventory
  2. Sort the compiled inventory

For the first part, you can just create a dictionary for that like:  

var a1 = [[2,"cafe"],[8,"water"],[2,"bola"],[2,"futebolball"],[2,"solarium"],[2,"pool"]]
var a2 = [[8,"cafe"],[3,"water"],[2,"futebolball"],[2,"solarium"],[2,"pool"]]

var dict : [String:Int] = [:]

a1.append(contentsOf: a2)

for row in a1 {
    let itemNumber = row[0] as! Int
    let itemName = row[1] as! String
    if dict[itemName] != nil {
        dict[itemName] = dict[itemName]! + itemNumber
    } else {
        dict[itemName] = itemNumber

and for the second part just a little FP here:  

print(dict.lazy.sorted { a1, a2 -> Bool in
    a1.key < a2.key
}.map { itemName, value -> [Any] in


Continue Algorithm Studying

If you like the solution for this inventory problem, you will probably like the “special palindrome problem”. There we use a two-pointer technique to traverse the array simultaneously from both sides.

Functional programming is a good technique to be familiar in algorithms because you can leverage your code using premade functions. For example in this solution for a “shopping cart” problem we use two functional operations to solve the whole problem.


That’s all my people, I hope you liked reading this article as much as I enjoyed writing it. If you want to support this blog you can Buy Me a Coffee or just leave a comment saying hello. You can also sponsor posts and I’m open to freelance writing! You can reach me on LinkedIn or Twitter and send me an e-mail through the contact page.

Thanks for reading and… That’s all folks.

Image Credit: Wikiart

Share this post:

Related posts