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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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.
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.
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bubbleSortfilterBoolschunkcountOccurrencesdeepFlattendifferenceduplicatesinsertionSortfisherYatesShufflecalcMediancalcBetterMedianaveragefactorialgcdlcm1lcm2maxnminnallUniquejustKeysjustValuescapitalizeFirstcapitalizeEveryWordcountVowelslowerCaseFirstLetterOfFirstWordisLowerCaseisUpperCasepalindromedrop
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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]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"]]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]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") //2Deep 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]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, pocahontasCheck 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"]) //trueInsertion 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]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]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]) //3Calculates 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) //3628800Calculates 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)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) //84Least 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]) //12Returns 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() //9Returns 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() //2One 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 ```⬆️ Back to top
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 4.5Checks 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"]) //falseFunction 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]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]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
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") //On A Scale From...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") //5Decapitalizes 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...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") //trueChecks 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") //falseReturns 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") //falseReturns 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)