unnamedd / 30-seconds-of-swift-code

A Swift implementation of 30-seconds-of-code: A curated collection of useful Swift 4 snippets that you can understand in 30 seconds or less.

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first-timers-onlyPRs Welcome

Welcome to 30-seconds-of-swift-code!

A Swift implementation of 30-seconds-of-code: A curated collection of useful Swift 4 snippets that you can understand in 30 seconds or less.

  • Use Ctrl + F or command + F to search for a snippet.

Note:- This is in no way affiliated with the original 30-seconds-of-code.

If you've come here from JavaScript land then you should be aware that this project uses Swift 4, therefore not all snippets will work as expected on every system. You'll need to check your Swift version by going to Project and then following the steps below.

version

If you need help installing the latest stable release of Swift 4 check out swift.org. If you run into trouble make sure you check out Stackoverflow.

This project contains plenty of useful snippets which can help beginners and newcomers quickly ramp-up their skills on Swift 4.

Table of contents

📚 List

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➗ Math

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🗃️ Object

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📜 String

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📚 List

bubble sort

BubbleSort is a sorting algorithm that uses the technique of repeatedly comparing and swapping the adjacent elements if they are in the wrong order.

func bubbleSort(_ inputArr:[Int]) -> [Int] {
    guard inputArr.count > 1 else {
        return inputArr
    }
    var res = inputArr
    let count = res.count
    var isSwapped = false
    repeat {
        isSwapped = false
        for index in stride(from: 1, to: count, by: 1) {
            if res[index] < res[index - 1] {
                res.swapAt((index - 1), index)
                isSwapped = true
            }
        }
    } while isSwapped
    return res
}
View Examples
bubbleSort([32,12,12,23,11,19,81,76]) //[11, 12, 12, 19, 23, 32, 76, 81]


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chunk

Chunks an array into smaller arrays of a certain size.

func chunk(arr: [Any], chunkSize: Int) -> [Any] {
    let chunks = stride(from: 0, to: arr.count, by: chunkSize).map {
        Array(arr[$0..<min($0 + chunkSize, arr.count)])
    }
    return chunks
}
View Examples
chunk(arr: [2, 4, 6, 8], chunkSize: 1) //[[2], [4], [6], [8]]
chunk(arr: [1, 3, 5, 9], chunkSize: 4) //[[1, 3, 5, 9]]
chunk(arr: ["hi", "yo", "bye", "bai"], chunkSize: 3) //[["hi", "yo", "bye"], ["bai"]]
chunk(arr: ["young", "scrappy", "hungry"], chunkSize: 2) //[["young", "scrappy"], ["hungry"]]


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filter bools

Remove every value that's not a Boolean.

func filterBools(_ inputArr: [Any]) -> [Any] {
    return inputArr.compactMap { $0 as? Bool }
    
}
View Examples
filterBools([false, 2, "lol", 3, "a", "s", 34, false, true]) //[false, false, true]


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count occurrences

Count occurrences of a string in an array.

func countOccurrences(arr: [String], into: String) -> Int {
    return arr.reduce(0) { $1 == into ? $0 + 1 : $0 }
}
View Examples
countOccurrences(arr: ["FOO", "FOO", "BAR"], into: "FOO") //2


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deep flatten

Deep flattens a list with recursion.

func deepFlatten(arr: [AnyHashable]) -> [AnyHashable] {
    var arr2 = [AnyHashable]()
    for el in arr {
        if let el = el as? Int {
            arr2.append(el)
        }
        if let el = el as? [Any] {
            let res = deepFlatten(arr: el as! [AnyHashable])
            for i in res {
                arr2.append(i)
            }
        }
    }
    return arr2
}
View Examples
deepFlatten(arr: [6, 5, 4, [3, 2], [1]]) //[6, 5, 4, 3, 2, 1]


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difference

Return element(s) not contained in both of the given arrays (ie. elements only contained in one array and not both.)

func difference(arr1: [AnyHashable], arr2: [AnyHashable]) -> Set<AnyHashable> {
    return Set(arr1).symmetricDifference(arr2)
}
View Examples
difference(arr1: [2, 4, 6, 8], arr2: [10, 8, 6, 4, 2, 0]) //10
difference(arr1: ["mulan", "moana", "belle", "elsa"], arr2: ["mulan", "moana", "belle", "pocahontas"]) //elsa, pocahontas


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duplicates

Check for duplicate elements in a given array.

func duplicates(arr1: [AnyHashable]) -> Bool {
    return arr1.count != (Set<AnyHashable>(arr1)).count
}
View Examples
duplicates(arr1: [5, 4, 3, 2]) //false
duplicates(arr1: ["hermione", "hermione", "ron", "harry"]) //true


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insertion sort

Insertion Sort algorithm--inspired by Ray Wenderlich https://github.com/raywenderlich/swift-algorithm-club/tree/master/Insertion%20Sort.

func insertionSort(_ array: [Int]) -> [Int] {
    var a = array             // 1
    for index in stride(from: 1, to: a.count, by: 1)  {
        var y = index
        while y > 0 && a[y] < a[y - 1] { // 3
            a.swapAt(y - 1, y)
            y -= 1
        }
    }
    return a
}
View Examples
let list = [ 10, -1, 3, 9, 2, 27, 8, 5, 1, 3, 0, 26 ]
insertionSort(list) //[-1, 0, 1, 2, 3, 3, 5, 8, 9, 10, 26, 27]


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fisher yates shuffle

Fisher-Yates algorithm aka Knuth shuffle to shuffle an array creates a uniform shuffle of the array where each permutation is equally likely in O(n) time.

func shuffle(arr1: [AnyHashable]) -> [AnyHashable] {
    var arr2 = arr1
    for i in stride(from: arr1.count - 1, through: 1, by: -1) {
        let j = Int.random(in: 0...i)
        if i != j {
            arr2.swapAt(i, j)
        }
    }
    return arr2
}
View Examples
var foo = [1,2,3]
shuffle(arr1: foo) //[2,3,1] , foo = [1,2,3]


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➗ Math

average

Returns the average of two or more doubles in an array.

func average(arr: [Double]) -> Double {
    return arr.reduce(0, +)/Double(arr.count)
}
View Examples
average(arr: [5, 4, 3, 2, 1]) //3


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factorial

Calculates the factorial of a number.

func factorial(num: Int) -> Int {
    var fact: Int = 1
    for index in stride(from: 1, to: num+1, by: 1) {
        fact = fact * index
    }
    return fact
}
View Examples
factorial(num: 4) //24
factorial(num: 10) //3628800


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gcd

Calculates the greatest common divisor between two integers with recursion.

func gcd(num1: Int, num2: Int) -> Int {
    let mod = num1 % num2
    if mod != 0 {
        return gcd(num1: num2, num2: mod)
    }
    return num2
}
View Examples
gcd(num1: 228, num2: 36) //12
gcd(num1: -5, num2: -10)


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lcm1

Returns the least common multiple of two integers using the gcd function above.

func lcm1(num1: Int, num2: Int) -> Int {
    return abs(num1 * num2) / gcd(num1: num1, num2: num2)
}
View Examples
lcm1(num1: 12, num2: 7) //84


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lcm2

Least common multiple of an array using the first lcm.

func lcm2(arr1: [Int]) -> Int {
    return arr1.reduce(1) { lcm1(num1: $0, num2: $1) }
}
View Examples
lcm2(arr1: [4, 3, 2]) //12


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max n

Returns the maximum element from the provided array.

func maxn(arr1: [Int]) -> Int {
    if let (_, maxValue) = arr1.enumerated().max(by: { $0.element < $1.element }) {
        return maxValue
    }
    return 0
}
View Examples
maxn(arr1: [2, 9, 5]) //9
[2, 9, 5].max() //9


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min n

Returns the minimum integer from an array without the built-in .min() function (used in examples to compare results.)

func minn(arr1: [Int]) -> Int {
    var minVal = arr1[0]
    for num in arr1 {
        minVal = (num  < minVal) ? num : minVal
    }
    return minVal
}
View Examples
minn(arr1: [8, 2, 4, 6]) //2
[8, 2, 4, 6].min() //2


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calc median

One way of calculating the median of an array of integers.

func calcMedian(arr: [Int]) -> Float {
    return Float(arr.sorted(by: <)[arr.count / 2])
}
View Examples ```swift calcMedian(arr: [1,2,3,4,5,6,7,8]) //returns 4.5 ```

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calc better median

Better way of calculating the median of an array of integers.

func calcBetterMedian(arr: [Int]) -> Float {
    let sorted = arr.sorted()
    if sorted.count % 2 == 0 {
        return Float((sorted[(sorted.count / 2)] + sorted[(sorted.count / 2) - 1])) / 2
    }
    return Float(sorted[(sorted.count - 1) / 2])
}
View Examples
calcBetterMedian(arr: [1,2,3,4,5,6,7,8]) //returns 4.5


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🗃️ Object

all unique

Checks a flat list for all unique values, returning True if list values are all unique and False if list values aren't all unique.

func allUnique(arr: [AnyHashable]) -> Bool {
    return arr.count == Set<AnyHashable>(arr).count
}
View Examples
allUnique(arr: [5, 4, 3, 2]) //true
allUnique(arr: ["lol", "rofl", "lol"]) //false


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just keys

Function which accepts a dictionary of key-value pairs and returns a new array of just the keys.

func justKeys(dict: Dictionary<AnyHashable, AnyHashable>) -> [AnyHashable] {
    return Array(dict.keys)
}
View Examples
var dict: Dictionary<String, String> = ["Mulan": "Mushu", "Anna": "Olaf", "Pocahontas": "Fleeko"]
justKeys(dict: dict) //[Anna, Mulan, Pocahontas]


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just values

Function which accepts a dictionary of key-value pairs and returns a new array of just the values.

func justValues(dict: Dictionary<AnyHashable, AnyHashable>) -> [AnyHashable] {
    return Array(dict.values)
}
View Examples
justValues(dict: dict) //[Olaf, Mushu, Fleeko]


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📜 String

capitalize first

Capitalizes the first letter of a string, leaving the rest the same.

func capitalizeFirst(str: String) -> String {
    var components = str.components(separatedBy: " ")
    components[0] = components[0].capitalized
    return components.joined(separator: " ")
}
View Examples
capitalizeFirst(str: "i like cheesE") //I like cheesE


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capitalize every word

Capitalizes the first letter of every word in a string.

func capitalizeEveryWord(str: String) -> String {
    return str.capitalized
}
View Examples
capitalizeEveryWord(str: "on a scale from 1 to 10 how would you rate your pain")


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count vowels

Retuns number of vowels in provided string.

func countVowels(str: String) -> Int {
    var vowelCount = 0
    let vowels = Set(["a", "e", "i", "o", "u"])
    for char in str.lowercased() {
        if vowels.contains("\(char)") {
            vowelCount += 1
        }
    }
    return vowelCount
}
View Examples
countVowels(str: "hi mom") //2
countVowels(str: "aeiou") //5


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lower case first letter of first word

Decapitalizes the first letter of the first word in a string.

func lowerCaseFirstLetterOfFirstWord(str: String) -> String {
    var components = str.components(separatedBy: " ")
    components[0] = components[0].lowercased()
    return components.joined(separator: " ")
}
View Examples
lowerCaseFirstLetterOfFirstWord(str: "Christmas Switch was a solid movie") //christmas Switch...


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is lower case

Return true if any character in a string is capitalized.

func isLowerCase(str: String) -> Bool {
    return str == str.lowercased()
}
View Examples
isLowerCase(str: "I LOVE CHRISTMAS") //false
isLowerCase(str: "<3 lol") //true


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is upper case

Checks that each character in a string is uppercase.

func isUpperCase(str: String) -> Bool {
    return str == str.uppercased()
}
View Examples
isUpperCase(str: "LOLOLOL") //true
isUpperCase(str: "lmao") //false
isUpperCase(str: "Rofl") //false


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palindrome

Returns True if the given string is a palindrome, False if otherwise.

func palindrome(str: String) -> Bool {
    return str.lowercased() == String(str.reversed()).lowercased()
}
View Examples
palindrome(str: "racecar") //true
palindrome(str: "Madam") //true
palindrome(str: "lizzie") //false


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drop

Returns a new array with n elements removed from the left.

func drop(arr: [AnyHashable], num: Int) -> [AnyHashable] {
    return Array(arr.dropFirst(num)) //need Array() to concert ArraySlice to Array
}
View Examples
drop(arr: [5, 4, 3, 2, 1, 0], num: 1)
drop(arr: ["Huey", "Dewey", "Louie"], num: 3)


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A Swift implementation of 30-seconds-of-code: A curated collection of useful Swift 4 snippets that you can understand in 30 seconds or less.


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