LESSON 194 OF 414 · NESTED LOOPS

Top K Brands V5 - Filter by Product in Scala

Practice

The full catalog covers many products. Filter to one product first, then rank the top k brands that sell it, using v4's repeated search on the filtered lists.

You start with:

        val products = Array("Laptop", "Phone", "Laptop", "Tablet", "Phone", "Laptop")
        val brands = Array("TechPro", "MegaCorp", "NeoByte", "Quantum", "Zenith", "AlphaTech")
        val ratings = Array(4, 5, 5, 3, 4, 4)
        val target = "Laptop"
        val k = 2

Build:

1. NeoByte (5)
2. TechPro (4)

Rules:

Filter: copy the brand and the rating of every row whose product equals target into two new lists, keeping the order.
From the filtered lists pick the top k by rating, highest first, with v4's repeated search. Ties go to the entry listed first.
If fewer than k products match, list only those that exist: when no brand is left, add no more lines (no extra lines, no error).
Each line is "rank. Brand (rating)", starting at rank 1.
Print the lines, one per line, with println(...).

Build filteredBrands and filteredRatings first: a loop over the catalog that copies the row when products(i) == target.

Then run v4's repeated search over the filtered lists (same code, new names).

If fewer than k products match, some round finds nobody (bestIndex stays -1): add a line only when a brand was found.

        val products = Array("Laptop", "Phone", "Laptop", "Tablet", "Phone", "Laptop")
        val brands = Array("TechPro", "MegaCorp", "NeoByte", "Quantum", "Zenith", "AlphaTech")
        val ratings = Array(4, 5, 5, 3, 4, 4)
        val target = "Laptop"
        val k = 2

        val filteredBrands = scala.collection.mutable.ArrayBuffer[String]()
        val filteredRatings = scala.collection.mutable.ArrayBuffer[Int]()
        for (i <- 0 until products.size) {
            if (products(i) == target) {
                filteredBrands.append(brands(i))
                filteredRatings.append(ratings(i))
            }
        }
        val used = Array.fill(filteredRatings.size)(false)
        val lines = scala.collection.mutable.ArrayBuffer[String]()
        for (rank <- 1 to k) {
            var bestIndex = -1
            for (i <- 0 until filteredRatings.size) {
                if (!used(i)) {
                    if (bestIndex == -1 || filteredRatings(i) > filteredRatings(bestIndex)) {
                        bestIndex = i
                    }
                }
            }
            if (bestIndex != -1) {
                used(bestIndex) = true
                lines.append(rank.toString() + ". " + filteredBrands(bestIndex) + " (" + filteredRatings(bestIndex) + ")")
            }
        }
        println(lines.mkString("\n"))

STEP 1 OF 18

Guided

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Top K Brands V5 - Filter by Product in Scala

Top K Brands V5 in Scala