Refactored Solution In Swift

Question

I\'ve been studying for a coding exam by doing the HackerRank test cases, for the most part I\'ve been doing well, but I get hung up on some easy cases and you all help me when

Answer 1

Thanks to @Alexander - I was able to solve this issue using NSCountedSet instead of my custom reduce method. It's much cleaner and more efficient. Here is the solution:

import Foundation

func main() -> String {
    let v = readLine()!.components(separatedBy: " ").map{Int($0)!}
    var a = [String](); var b = [String]()
    if v[0] < v[1] { return "No"}
    for i in 0 ..< 2 {
        if i == 0 {
            a = (readLine()!).components(separatedBy: " ")
        } else { b = (readLine()!).components(separatedBy: " ") }
    }
    let countA = NSCountedSet(array: a)
    let countB = NSCountedSet(array: b)
    let intersect = Set(a).intersection(Set(b))
    let check = intersect.map{ countB.count(for: $0) <= countA.count(for: $0) }
    return !check.contains(false) ? "Yes" : "No"
}
print(main())

Many thanks!

Answer 2

I took the leisure of making some improvements on your code. I put comments to explain the changes:

import Foundation

func main() -> String {
    // Give more meaningful variable names
    let firstLine = readLine()!.components(separatedBy: " ").map{Int($0)!}
    let (magazineWordCount, ransomNoteWordCount) = (firstLine[0], firstLine[1])

    // a guard reads more like an assertion, stating the affirmative, as opposed to denying the negation.
    // it also 
    guard magazineWordCount > ransomNoteWordCount else { return "No" }

    // Don't use a for loop if it only does 2 iterations, which are themselves hardcoded in.
    // Just write the statements in order.
    let magazineWords = readLine()!.components(separatedBy: " ")
    let ransomNoteWords = readLine()!.components(separatedBy: " ") //You don't need ( ) around readLine()!

    let magazineWordCounts = NSCountedSet(array: magazineWords)
    let ransomNoteWordCounts = NSCountedSet(array: ransomNoteWords)

    // intersect is a verb. you're looking for the noun, "intersection"
    // let intersection = Set(a).intersection(Set(b))
    // let check = intersect.map{ countB.count(for: $0) <= countA.count(for: $0) }

    // You don't actually care for the intersection of the two sets.
    // You only need to worry about exactly the set of words that
    // exists in the ransom note. Just check them directly.
    let hasWordWithShortage = ransomNoteWordCounts.contains(where: { word in
       magazineWordCounts.count(for: word) < ransomNoteWordCounts.count(for: word)
    })

    // Don't negate the condition of a conditional expression. Just flip the order of the last 2 operands.
    return hasWordWithShortage ? "No" : "Yes"
}
print(main())

with the comments removed:

import Foundation

func main() -> String {
    let firstLine = readLine()!.components(separatedBy: " ").map{Int($0)!}
    let (magazineWordCount, ransomNoteWordCount) = (firstLine[0], firstLine[1])

    guard magazineWordCount > ransomNoteWordCount else { return "No" }

    let magazineWords = readLine()!.components(separatedBy: " ")
    let ransomNoteWords = readLine()!.components(separatedBy: " ")

    let magazineWordCounts = NSCountedSet(array: magazineWords)
    let ransomNoteWordCounts = NSCountedSet(array: ransomNoteWords)

    let hasWordWithShortage = ransomNoteWordCounts.contains{ word in
       magazineWordCounts.count(for: word) < ransomNoteWordCounts.count(for: word)
    }

    return hasWordWithShortage ? "No" : "Yes"
}
print(main())

It's simpler, and much easier to follow. :)