HackerRank [Swift] 1 Month Preparation Kit - Week 2

01_SalesByMatch.swift

import Foundation

func sockMerchant(n: Int, ar: [Int]) -> Int {
    var sockBag: Set<Int> = []
    var totalPairs: Int = 0
    
    for sock in ar{
        if sockBag.contains(sock){
           sockBag.remove(sock)
           totalPairs += 1
           continue
        }
        sockBag.insert(sock)
    }
    
    return totalPairs
}

02_ZigZagSequence.swift

import UIKit

func findZigZagSequence(arr: [Int], n: Int) -> [Int]{
    var sortedArray: [Int] = arr
    sortedArray.sort()
    let mid: Int = ((n+1)/2)-1
    var start: Int = mid + 1
    var end: Int = n - 2
    var holder: Int = 0
    
    holder = sortedArray[mid]
    sortedArray[mid] = sortedArray[n-1]
    sortedArray[n-1] = holder
    
    while start <= end{
        holder = sortedArray[start]
        sortedArray[start] = sortedArray[end]
        sortedArray[end] = holder
        start += 1
        end -= 1
    }
    
    print(sortedArray)
    return sortedArray
}

03_DrawingBook.swift

import Foundation

// V 2.0
struct Book{
    var normalBook: [[Int]] = []
    var reversedBook: [[Int]] {
        get {
            return normalBook.reversed()
        }
        set(newBook) {
            normalBook = newBook
        }
    }
    
    init(numberOfPages pages: Int) {
        var i: Int = 0
        
        while i <= pages{
            normalBook += [[i,i+1]]
            i += 2;
        }
    }
}

func pageCount(n: Int, p: Int) -> Int {
    let book: Book = Book(numberOfPages: n)
        
    return minPageFlipsToOpenA(Book: book, OnPage: p)
}

func minPageFlipsToOpenA(Book book: Book, OnPage page: Int) -> Int{
    var pageFlips: Int = 0
    
    for pages in book.normalBook{
        if pages.contains(page){
            pageFlips = book.normalBook.firstIndex(of: pages)!
            break
        }
    }
    
    for pages in book.reversedBook{
        if pages.contains(page){
            pageFlips = pageFlips < book.reversedBook.firstIndex(of: pages)! ? pageFlips : book.reversedBook.firstIndex(of: pages)!
            break
        }
    }
    
    return pageFlips
}

pageCount(n:5, p:4)




// V 1.0
func originalPageCount(n: Int, p: Int) -> Int {
    var book: [[Int]] = []
    var i: Int = 0
    var pageFlips: Int = 0
    var reverseFlips: Int = 0

    // Inicializamos el libro
    while i <= n{
        book += [[i,i+1]]
        i += 2;
    }

    for pages in book{
        if pages.contains(p){
            pageFlips = book.firstIndex(of: pages)!
            break
        }
    }

    book.reverse()
    for pages in book{
        if pages.contains(p){
            reverseFlips = book.firstIndex(of: pages)!
            break
        }
    }

    return (pageFlips < reverseFlips ? pageFlips : reverseFlips)
}

04_TowerBreakers.swift

import Foundation

func towerBreakers(n:Int, m:Int) -> Int{
    var winner: Int = 0
    let evenTowers: Bool = n.isMultiple(of: 2)
    switch evenTowers{
        case true:
            winner = 2
            break
        case false:
            winner = m > 1 ? 1 : 2
            break
    }
    return winner
}

05_CaesarsCipher.swift

import Foundation

//I'm sure there's  a fancier way to do this...
func caesarCipher(s: String, k: Int) -> String {
    var cipheredText    : String    = ""
    let alphaList                   = Array("abcdefghijklmnopqrstuvwxyz")
    var cipheredLetter  : Character
    var cipherIdx       : Int?      = 0
    var isUpperCase     : Bool      = false
    var shiftLetter     : Character = Character("a")
    
    for letter in s{
        isUpperCase = letter.isUppercase
        shiftLetter = isUpperCase ? Character(letter.lowercased()) : letter
        cipherIdx = alphaList.firstIndex(of: shiftLetter)
        if cipherIdx != nil{
            cipheredLetter = isUpperCase ? Character(alphaList[(cipherIdx!+k)%alphaList.count-1].uppercased()) : alphaList[(cipherIdx!+k)%alphaList.count-1]
            cipheredText.append(cipheredLetter)
            continue
        }
        cipheredText.append(letter)
    }
    
    return cipheredText
}