Collection-Types-Sets.md

Sets Exercises

Question One

Create a new array numbersWithNoDuplicates that has all of the elements from numbers without any duplicates. It should be in the same order as the original.

let numbers = [1,1,2,4,4,4,6,6,7,8]

var numbersWithNoDuplicates = [Int]()

// expected output: [1, 2, 4, 6, 7, 8]

// Your code here

Solution

let numbers = [1,1,2,4,4,4,6,6,7,8]

var numbersWithNoDuplicates = [Int]()

var set: Set<Int> = []

for num in numbers {
  if !set.contains(num) {
    numbersWithNoDuplicates.append(num)
    set.insert(num)
  }
}

print(numbersWithNoDuplicates) // [1, 2, 4, 6, 7, 8]

---

Questions Two

Create a new array scoresThatAppearOnce that has all the elements from scores that appear exactly once. It should be in the same order as the original.

let scores = [1, 77, 83, 32, 77, 77, 83, 32, 99]

var scoresThatAppearOnce = [Int]()

// expected output: [1, 99]

// Your code here

Solution

let scores = [1, 77, 83, 32, 77, 77, 83, 32, 99]

var scoresThatAppearOnce = [Int]()

var visited: Set<Int> = []

var freqDict = [Int: Int]()
scores.forEach { freqDict[$0, default: 0] += 1 }

for score in scores {
  if freqDict[score] == 1 {
    scoresThatAppearOnce.append(score)
  }
}

print(scoresThatAppearOnce) // [1, 99]

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Question Three

a. Given arrOne and arrTwo, create a variable arrThree which is equal to the UNION of arrOne and arrTwo. It should not contain any duplicate elements. Sort arrThree from smallest to greatest.

let arrOne = [1,2,3,4,5]
let arrTwo = [3,4,5,6,7]

var arrThree: [Int] = []

// expected output: [1, 2, 3, 4, 5, 6, 7]

// Your code here

Solution

let arrOne = [1,2,3,4,5]
let arrTwo = [3,4,5,6,7]

var arrThree: [Int] = []

arrThree = Array(Set(arrOne).union(Set(arrTwo))).sorted()

print(arrThree) // [1, 2, 3, 4, 5, 6, 7]

b. Given arrFour and arrFive, create a variable arrSix with is equal to the INTERSECTION of arrFour and arrFive. If should not contain any duplicate elements. Sort arrSix from smallest to greatest.

let arrFour = [1,2,3,4,5]
let arrFive = [3,4,5,6,7]

var arrSix: [Int] = []

// expected output: [3, 4, 5]

// Your code here

Solution

let arrFour = [1,2,3,4,5]
let arrFive = [3,4,5,6,7]

var arrSix: [Int] = []

arrSix = Array(Set(arrFour).intersection(Set(arrFive))).sorted()

print(arrSix) // [3, 4, 5]

---

Question Four

Given the 4 arrays of Ints below, create a new array, sorted in ascending order, that contains all the values without duplicates.

let numsOne = [2, 4, 5, 6, 8, 10, 12]
let numsTwo = [1, 2, 3, 4, 5, 6]
let numsThree = [5, 6, 7, 8, 9, 10, 11, 12]
let numsFour = [1, 3, 4, 5, 6, 7, 9]

var allNumsWithNoDuplicates: [Int] = []

// expected output: [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12]

// Your code here

Solution

let numsOne = [2, 4, 5, 6, 8, 10, 12]
let numsTwo = [1, 2, 3, 4, 5, 6]
let numsThree = [5, 6, 7, 8, 9, 10, 11, 12]
let numsFour = [1, 3, 4, 5, 6, 7, 9]

var allNumsWithNoDuplicates: [Int] = []

allNumsWithNoDuplicates = Array(Set(numsOne + numsTwo + numsThree + numsFour)).sorted()

print(allNumsWithNoDuplicates) // [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12]

---

Question Five

Roy wanted to increase his typing speed for programming contests. His friend suggested that he type the sentence The quick brown fox jumps over the lazy do repeatedly. This sentence is known as a pangram because it contains every letter of the alphabet.

After typing the sentence several times, Roy became bored with it so he started to look for other pangrams.

Given a sentence, determine whether it is a pangram. Ignore case.

Full question on HackerRank

Solution

func pangrams(s: String) -> String {
  let alphabets = Set("abcdefghijklmnopqrstuvwxyz")
  let set = Set(s.replacingOccurrences(of: " ", with: "").lowercased())
  guard set.count == 26 else {
    return "not pangram"
  }
  return alphabets == set ? "pangram" : "not pangram"
}

pangrams(s: "We promptly judged antique ivory buckles for the next prize") // pangram
pangrams(s: "We promptly judged antique ivory buckles for the prize") // not pangram