questions7.md

Topics covered

• Arrays
• Type extensions
• Using zip

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Question 1

Zip Problem: Use zip to enumerate another list

Example:

method(arr: ["a","b","c","d"]) // outputs "a : 1", "b : 2", ...

Solution:

let numArr: [Int] = [1,2,3,4,5,6]
let letterArr: [String] = ["A","B","C","D","E","F"]

for (num, letter) in zip(numArr, letterArr) {
    print("\(num,letter)")
}

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Question 2

Round a decimal to a specified level of precision round(double * (places of precision ex: 10 = 2, 100 = 3))

Solution:

let double: Double = 4.59
let rounded = round(double * 10) / 10

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Question 3

Create an extension to reverse a number

Example:

-123.reverse() // returns -321

Solution:

let nums = -123

let numStr = "\(nums)"
let splitIndex = numStr.index(numStr.startIndex, offsetBy: 1)
let range1 = numStr.startIndex..<splitIndex
let range2 = splitIndex..<numStr.endIndex
print(numStr[range1] + numStr[range2].reversed() + (nums % 2 == 0 ? "even" : " not even"))



extension Int {
    func reverse() -> Int {
        let numStr = "\(self)"
        let splitIndex = numStr.index(numStr.startIndex, offsetBy: 1)
        let range = splitIndex..<numStr.endIndex
        let reversedNumStr = "-\(String(numStr[range].reversed()))"
        return Int(reversedNumStr)!
    }
}
let nums2 = -524 // return -425
print(nums2.reverse())

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Question 4

Take an array of strings, double them and filter out the ones that are longer than 6 characters

Solution:

extension String {
    func double() -> String {
        return self + self
    }

    func length() -> Int {
        return characters.count
    }
}

let strArr: [String] = ["A", "Cat", "Jumped", "Else", "Football", "Tinder", "Boy", "Girl", "Do", "It"]
print(strArr.filter { $0.length() < 3 }.map { $0.double() })

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Question 5

Given an array, return it with only unique elements

Solution:

let array1: [String] = ["An", "Apple", "Is", "A", "Fruit", "Apple"]

func uniqueEle(_ arr: [String]) -> [String] {
    var elements = Set<String>()
    for element in arr {
        elements.insert(element)
    }
    return Array(elements)
}

print(uniqueEle(array1))

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