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Collection Types - Array Exercises

Question 1

Create an array of strings called colors that contain "orange", "red", "yellow", "turquoise", and "lavender".

Then, using array subscripting and string interpolation, print out the String "orange, yellow, and lavender are some of my favorite colors".

Solution 
var colors = ["orange", "red", "yellow", "turquoise", "lavender"]

print("\(colors[0]), \(colors[2]) and \(colors[colors.count - 1]) are some of my favorite colors")

// orange, yellow and lavender are some of my favorite colors

Question 2

Remove "Illinois" and "Kansas" from the array below.

var westernStates = ["California", "Oregon", "Washington", "Idaho", "Illinois", "Kansas"]

Solution 
var westernStates = ["California", "Oregon", "Washington", "Idaho", "Illinois", "Kansas"]
westernStates = westernStates.dropLast(2)
print(westernStates) // ["California", "Oregon", "Washington", "Idaho"]

Question 3

Iterate through the array below. For each state, print out the name of the state, a colon, and whether it is or is not in the continental United States.

let moreStates = ["Hawaii", "New Mexico", "Alaska", "Montana", "Texas", "New York", "Florida"]

Solution 
let moreStates = ["Hawaii", "New Mexico", "Alaska", "Montana", "Texas", "New York", "Florida"]

for state in moreStates {
  if state == "Hawaii" {
    print("\(state) is NOT in the continental United States.")
  } else {
    print("\(state) is in the continental United States.")
  }
}

/*
 Hawaii is NOT in the continental United States.
 New Mexico is in the continental United States.
 Alaska is in the continental United States.
 Montana is in the continental United States.
 Texas is in the continental United States.
 New York is in the continental United States.
 Florida is in the continental United States.
*/

Question 4

Print out how many non-whitespace characters are in myString:

let myString = "This is good practice with Strings!"

Solution 
let myString = "This is good practice with Strings!"

var nonWhitespaceCount = 0
for char in myString {
  if char != " " {
    nonWhitespaceCount += 1
  }
}
print("There are \(nonWhitespaceCount) non-whitespace characters in myString")
// There are 30 non-whitespace characters in myString

Iterate through the array below. For each sentence, print out how many non-whitespace characters are in it.

let myFavoriteQuotes = ["To be or not to be, that is the question.", "The only source of knowledge is experience.", "Mr. Gorbachev, tear down this wall!", "Four score and twenty years ago..."]

Solution 
let myFavoriteQuotes = ["To be or not to be, that is the question.", "The only source of knowledge is experience.", "Mr. Gorbachev, tear down this wall!", "Four score and twenty years ago..."]


for str in myFavoriteQuotes {
  var nonWhitespaceCount = 0
  for char in str {
    if char != " " {
      nonWhitespaceCount += 1
    }
  }
  print("There are \(nonWhitespaceCount) non-whitespace characters in myString")
}

/*
 There are 32 non-whitespace characters in myString
 There are 37 non-whitespace characters in myString
 There are 30 non-whitespace characters in myString
 There are 29 non-whitespace characters in myString
*/

Question 5

Iterate through garden and place any 🌷 that you find into the basket. Replace any 🌷 that you pick up with "dirt". Then print how many 🌷 are in your basket.

var garden = ["dirt","🌷","dirt","🌷","dirt","dirt","🌷","dirt","🌷","dirt"]
var basket = [String]()
Solution 
var garden = ["dirt","🌷","dirt","🌷","dirt","dirt","🌷","dirt","🌷","dirt"]
var basket = [String]()


for (index, str) in garden.enumerated() {
  if str == "🌷" {
    basket.append("🌷")
    garden[index] = "dirt"
  }
}

print(garden)
print("The basket now has \(basket.count) flowers 🌷")

/*
 ["dirt", "dirt", "dirt", "dirt", "dirt", "dirt", "dirt", "dirt", "dirt", "dirt"]
 The basket now has 4 flowers 🌷
*/

Question 6

The below array represents an unfinished batting lineup for a baseball team. You, the coach, need to make some last minute changes:

  • Add "Suzuki" to the end of your lineup.
  • Change "Jeter" to "Tejada".
  • Change "Thomas" for "Guerrero"
  • Put "Reyes" to bat 8th instead.

var battingLineup = ["Reyes", "Jeter", "Ramirez", "Pujols","Griffey","Thomas","Jones", "Rodriguez"]

Solution 
var battingLineup = ["Reyes", "Jeter", "Ramirez", "Pujols","Griffey","Thomas","Jones", "Rodriguez"]

battingLineup.append("Suzuki")

for (index, player) in battingLineup.enumerated() {
  if player == "Jeter" {
    battingLineup[index] = "Tejada"
  }
  if player == "Thomas" {
    battingLineup[index] = "Guerrero"
  }
}

if let index = battingLineup.firstIndex(of: "Reyes") {
  battingLineup.remove(at: index)
  battingLineup.insert("Reyes", at: 7)
}

print(battingLineup)

// ["Tejada", "Ramirez", "Pujols", "Griffey", "Guerrero", "Jones", "Rodriguez", "Reyes", "Suzuki"]

Question 7

Given an array of Ints, find out if it contains a target number.

(The built-in contains(_:) function will do this, but you aren't allowed to use it for this exercise.)

var numbers: [Int]

let target: Int = 32

Ex.1

numbers = [4,2,6,73,32,4,2,1]

target = 32

//true
Solution 
let numbers = [4,2,6,73,32,4,2,1]
let target = 32

var targetNumberFound = false
for num in numbers {
  if num == target {
    targetNumberFound = true
  }
}

print(targetNumberFound) // true

Ex. 2

numbers = [32459,2,4,5,1,4,2,1]

target = 3

//false
Solution 
let numbers = [32459,2,4,5,1,4,2,1]
let target = 3

var targetNumberFound = false
for num in numbers {
  if num == target {
    targetNumberFound = true
  }
}

print(targetNumberFound) // true

Question 8

Find the largest value in an array of Int. Do not use the built-in max() method.

let arrayOfNumbers: [Int] = (1...100).map{ _ in Int.random(in: 0...200)}.map{Int($0)}

//This creates an array of 100 numbers in between 0 and 200.  For now, you don't need to worry about how it does that.
Solution 
let arrayOfNumbers: [Int] = (1...100).map{ _ in Int.random(in: 0...200)}.map{Int($0)}

print(arrayOfNumbers)

var largestValue = arrayOfNumbers[0]
for num in arrayOfNumbers {
  if num > largestValue {
    largestValue = num
  }
}

print("largest value is \(largestValue)")
// largest value is 199

Question 9

Find the smallest value in an array of Int. Do not use the built in min() method.

let arrayOfNumbers: [Int] = (1...100).map{ _ in Int.random(in: 0...200)}.map{Int($0)}

//This creates an array of 100 numbers in between 0 and 200.  For now, you don't need to worry about how it does that.
Solution 
let arrayOfNumbers: [Int] = (1...100).map{ _ in Int.random(in: 0...200)}.map{Int($0)}

print(arrayOfNumbers)

var smallestValue = arrayOfNumbers[0]
for num in arrayOfNumbers {
  if num < smallestValue {
    smallestValue = num
  }
}

print("smallest value is \(smallestValue)")
// smallest value is 0

Question 10

Iterate through secondListOfNumbers, and print out all the odd numbers.

var secondListOfNumbers = [19,13,14,19,101,10000,141,404]

Solution 
var secondListOfNumbers = [19, 13, 14, 19, 101, 10000, 141, 404]

for num in secondListOfNumbers {
  if num % 2 == 1 {
    print(num, terminator: " ")
  }
}

// 19 13 19 101 141

Question 11

Iterate through thirdListOfNumbers, and print out the sum.

var thirdListOfNumbers = [11, 26, 49, 61, 25, 40, 74, 3, 22, 23]

Solution 
var thirdListOfNumbers = [11, 26, 49, 61, 25, 40, 74, 3, 22, 23]
var sum = 0

for num in thirdListOfNumbers {
  sum += num
}

print(sum) // 334

Question 12

Iterate through thirdListOfNumbers, and print out the sum of all the even numbers.

var thirdListOfNumbers = [11, 26, 49, 61, 25, 40, 74, 3, 22, 23]

Solution 
var thirdListOfNumbers = [11, 26, 49, 61, 25, 40, 74, 3, 22, 23]
var sum = 0

for num in thirdListOfNumbers {
  if num % 2 == 0 {
    sum += num
  }
}

print(sum) // 162

Question 13

Append every Int that appears in both listOne and listTwo to the sharedElements array. Then print how many Ints are shared.

Assumption: both arrays are of equal length.

Constraints: you cannot use Sets

var listOne = [28, 64, 7, 96, 13, 32, 94, 11, 80, 68]
var listTwo = [18, 94, 48, 6, 42, 68, 79, 76, 13, 7]
var sharedElements = [Int]()
Solution 
var listOne = [28, 64, 7, 96, 13, 32, 94, 11, 80, 68]
var listTwo = [18, 94, 48, 6, 42, 68, 79, 76, 13, 7]
var sharedElements = [Int]()


for num in listOne {
  if listTwo.contains(num) {
    sharedElements.append(num)
  }
}

print("\(sharedElements) \(sharedElements.count) are shared")

// [7, 13, 94, 68] 4 are shared

Question 14

Write code such that noDupeList has all the same Ints as dupeFriendlyList, but has no more than one of each Int.

Constraints: you cannot use Sets

var dupeFriendlyList = [4,2,6,2,2,6,4,9,2,1]
var noDupeList: [Int] = []
Solution 
var dupeFriendlyList = [4,2,6,2,2,6,4,9,2,1]
var noDupeList: [Int] = []

for num in dupeFriendlyList {
  if !noDupeList.contains(num) {
    noDupeList.append(num)
  }
}

print(noDupeList)

Question 15

Find the second smallest number in an Array of Ints

let arrayOfNumbers = [-6, 13, 0, 34, 0, 45, -12, 9, 11, 4]

Solution 
let arrayOfNumbers = [-6, 13, 0, 34, 0, 45, -12, 9, 11, 4]

var secondSmallest = Int.max
var smallest = Int.max

for num in arrayOfNumbers {
  if num < smallest {
    secondSmallest = smallest
    smallest = num
  } else if num < secondSmallest && num != smallest {
    secondSmallest = num
  }
}

print(smallest, secondSmallest) // -12, -6

Question 16

If we list all the natural numbers below 10 that are multiples of 3 or 5, we get 3, 5, 6 and 9. The sum of these multiples is 23.

Find the sum of all the multiples of 3 or 5 below 1000.

Solution 
var multiples = [Int]()
for num in 1..<1000 {
  if num % 3 == 0 || num % 5 == 0 {
    multiples.append(num)
  }
}

print(multiples)