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Collection-Types-Dictionaries.md

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Collection Types - Dictionary Exercise

Question 1

var applesDict: [String: Int] = ["Adam": 3,
                                 "Beth": 5,
                                 "Cal": 3,
                                 "Dan": 5,
                                 "Eve": 4]

a. Set eveAppleCount equal to the number of apples that Eve has

let eveAppleCount =
Solution 
let eveAppleCount = applesDict["Eve"] ?? 0
print(eveAppleCount) // 4

b. Change the number of apples that Adam has to 4

// Your code here

Solution 
applesDict["Adam"] = 4
print(applesDict["Adam"] ?? 0) // 4

c. Set calAndDanAppleCount equal to the sum of Cal and Dan

let calAndDanAppleCount = 

// Expected output: 8
Solution 
let calAndDanAppleCount = (applesDict["Cal"] ?? 0) + (applesDict["Dan"] ?? 0)
print(calAndDanAppleCount) // 8

d. Set all the values in applesDict to 0

// Your code here

Solution 
applesDict.forEach { applesDict[$0.key] = 0 }
print(applesDict) // ["Cal": 0, "Dan": 0, "Beth": 0, "Adam": 0, "Eve": 0]

Question Two

var citiesDict: [String: String] = ["Afghanistan": "Kabul",
                                    "Russia": "Moscow",
                                    "Iceland": "Reykjavik"]

a. Set russiaCapital equal to Russia's capital using citiesDict

let russiaCapital = /* Your code here (Replace "" with your solution)*/ ""

// Your code here

Solution 
let russiaCapital = citiesDict["Russia"] ?? ""
print(russiaCapital) // Moscow

b. Add a new key value pair "Jamaica" and its capital "Kingston"

// Your code here

Solution 
citiesDict["Jamaica"] = "Kingston"
print(citiesDict)
// ["Russia": "Moscow", "Jamaica": "Kingston", "Iceland": "Reykjavik", "Afghanistan": "Kabul"]

c. Add a new key value pair "Indonesia" and its capital "Jakarta"

// Your code here

Solution 
citiesDict["Indonesia"] = "Jakarta"
print(citiesDict)
// ["Russia": "Moscow", "Jamaica": "Kingston", "Indonesia": "Jakarta", "Iceland": "Reykjavik", "Afghanistan": "Kabul"]

Question 3

a. Create a dictionary that represents the table below listing an authors name and their comprehensibility score.

/*
| Author Name |    Score |
| :--: | :--: |
| Mark Twain |    8.9 |
| Nathaniel Hawthorne    | 5.1 |
| John Steinbeck    | 2.3 |
| C.S. Lewis | 9.9 |
| Jon Krakauer | 6.1 |
*/

var authorScores = [String: Double] ()

/*
Expected outputs: 
["Mark Twain": 8.9, "John Steinbeck": 2.3, "Jon Krakauer": 6.1, " C.S. Lewis": 9.9, "Nathaniel Hawthorne": 5.1]
*/

// Your code here

Solution 
authorsScores = ["Mark Twain": 8.9, "Nathaniel Hawthorne": 5.1, "John Steinbeck": 2.3, " C.S. Lewis": 9.9, "Jon Krakauer": 6.1]

print(authorsScores)
// ["Mark Twain": 8.9, "John Steinbeck": 2.3, "Jon Krakauer": 6.1, " C.S. Lewis": 9.9, "Nathaniel Hawthorne": 5.1]

b. Add an additional author named “Erik Larson” with an assigned score of 9.2.

Solution 
authorsScores["Erik Larson"] = 9.2

print(authorsScores)
// ["Mark Twain": 8.9, "John Steinbeck": 2.3, "Erik Larson": 9.2, "Jon Krakauer": 6.1, " C.S. Lewis": 9.9, "Nathaniel Hawthorne": 5.1]

Question Four

You are given an array of dictionaries. Each dictionary in the array describes the score of a person. Find the person with the best score and print his full name.

var peopleWithScores: [[String: String]] = [
    [
        "firstName": "Calvin",
        "lastName": "Newton",
        "score": "13"
    ],
    [
        "firstName": "Garry",
        "lastName": "Mckenzie",
        "score": "23"
    ],
    [
        "firstName": "Leah",
        "lastName": "Rivera",
        "score": "10"
    ],
    [
        "firstName": "Sonja",
        "lastName": "Moreno",
        "score": "3"
    ],
    [
        "firstName": "Noel",
        "lastName": "Bowen",
        "score": "16"
    ]
]

var highestScoringName = ""

// Expected output: "Garry Mckenzie"
// Your code here
Solution 
var highestScoringName = ""
var highestScore = 0
for scoreDict in peopleWithScores {
  if let scoreStr = scoreDict["score"],
     let score = Int(scoreStr),
     let firstName = scoreDict["firstName"],
     let lastName = scoreDict["lastName"] {
    if score > highestScore {
      highestScore = score
      highestScoringName = firstName + " " + lastName
    }
  }
}

print(highestScoringName) // Garry Mckenzie

Question Five

Write code below such that cubeDict maps the numbers between 1 and 20 inclusive to their cubes. A number's cube is that number multiplied by itself twice:

2 ^ 3 = 2 * 2 * 2 = 8
var cubeDict = [Int: Int]()

/*
 Sample output:
 
 cubeDict.count // 20
 cubeDict[2] // 8
 cubeDict[3] // 27
 cubeDict[20] // 8000
 cubeDict[14] // 2744
*/

// Your code here

Solution 
var cubeDict = [Int: Int]()

for num in 1...20 {
  cubeDict[num] = num * num * num
}

print(cubeDict.count) // 20
print(cubeDict)
// [10: 1000, 3: 27, 7: 343, 12: 1728, 9: 729, 5: 125, 17: 4913, 18: 5832, 19: 6859, 20: 8000, 13: 2197, 8: 512, 6: 216, 1: 1, 4: 64, 16: 4096, 11: 1331, 15: 3375, 14: 2744, 2: 8]

Question Six

Find the most common letter in the string below. Use a dictionary to generate your solution that maps a character to the number of times it appears in the string. Ignore whitespaces and capitalization.

let myString = "We're flooding people with information. We need to feed it through a processor. A human must turn information into intelligence or knowledge. We've tended to forget that no computer will ever ask a new question."

var frequencyDict = [Character: Int]()
var mostFrequentChar: Character = "?"

// Excpected output: "e"

// Your code here

Solution 
let myString = "We're flooding people with information. We need to feed it through a processor. A human must turn information into intelligence or knowledge. We've tended to forget that no computer will ever ask a new question."

var frequencyDict = [Character: Int]()
var mostFrequentChar: Character = "?"

for char in myString {
  if !char.isWhitespace && !char.isUppercase {
    if let count = frequencyDict[char] {
      frequencyDict[char] = count + 1
    } else {
      frequencyDict[char] = 1
    }
  }
}

let maxElement = frequencyDict.max { $0.value < $1.value }
mostFrequentChar = maxElement?.key ?? " "
print(mostFrequentChar) // e