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.
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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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bubbleSortfilterBoolschunkcountOccurrencesdeepFlattendifferenceduplicatesevery_nthinsertionSortfisherYatesShufflecalcMediancalcBetterMedianaveragefactorialgcdlcm1lcm2maxnminnallUniquejustKeysjustValuesbytesFromStringcapitalizeFirstcapitalizeEveryWordcountVowelslowerCaseFirstLetterOfFirstWordisLowerCaseisUpperCasepalindromeanagramdropdropRightWhilenthElementfilterNonUniquegenericFlattencommaSeparatedmostFrequentrepeating
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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"]]Returns every nth element in a given list and a new list is created that contains every nth element of the given list.
func getEvery( nth: Int, from list: [Any] ) {
var nthElements = [Any]()
var shiftedList = list
shiftedList.insert(0, at: 0)
for (i, element) in shiftedList.enumerated() {
if i > 0 && i.isMultiple(of: nth) {
nthElements.append(element)
}
}
}View Examples
getEvery(nth: 4, from: ["The", "quick", "brown", "fox", "jumped", "over", "the", "lazy", "dog"]) //["fox", "lazy"]
getEvery(nth: 2, from: [1,2,3,4,5,6,7,8,9]) //[2, 4, 6, 8]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]Link to Official Apple Developer Documentation - https://developer.apple.com/documentation/swift/array/1688499-sort
var integerArray = [5,8,2,3,656,9,1]
var stringArray = ["India", "Norway", "France", "Canada", "Italy"]
integerArray.sort() //[1, 2, 3, 5, 8, 9, 656]
stringArray.sort() //["Canada", "France", "India", "Italy", "Norway"]View Examples
integerArray.sort() //[1, 2, 3, 5, 8, 9, 656]
stringArray.sort() //["Canada", "France", "India", "Italy", "Norway"]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]Takes an array of arrays as input and transforms it to a flattened array of its type. ( handles optionals )
/// We use flat map to flatten the array and compact map to handle optionals
/// - Parameter arrays: Array of arrays to flatten
func flatten<T>(arrays: [[T?]]) -> [T] {
return arrays.flatMap{$0}.compactMap{$0}
}View Examples
flatten(arrays: [["a","b","c","d"],["e","f","g","y"]]) // ["a", "b", "c", "d", "e", "f", "g", "y"]
flatten(arrays: [[1,nil,3,4],[5,6,7,8]]) // [1, 3, 4, 5, 6, 7, 8]Takes an array of strings and returns a single string with each element from the input list separated by commas.
/// Return the elements of `strings` separated by ", "
func commaSeparated(_ strings: [String]) -> String {
return strings.joined(separator: ", ")
}View Examples
let strs = ["Foo", "Bar", "Baz", "Qux"]
commaSeparated(strs) // "Foo, Bar, Baz, Qux"Takes an array and returns the most frequent element that appears in the array. The type of elements in the array must conform hashable.
// Return the most frequent element that appears in the array
func mostFrequent<Type: Hashable>(_ arr: [Type]) -> Type? {
var dict = [Type: Int]()
for element in arr {
if dict[element] == nil {
dict[element] = 1
} else {
dict[element]! += 1
}
}
return dict.sorted(by: { $0.1 > $1.1 }).first?.key
}View Examples
mostFrequent([1, 2, 5, 4, 1, 9, 8, 7, 4, 5, 1, 5, 1]) // 1
mostFrequent(["a", "b", "c", "a"]) // "a"
mostFrequent([]) // nilReturns 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 4.5Convert an angle from radians to degrees.
func radiansToDegrees(_ angle: Double) -> Double {
return angle * 180 / .pi
}View Examples
radiansToDegrees(4) // 229.183Checks 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]Get bytes of a string.
func bytes(_ str: String) -> Int {
return str.utf8.count
}View Examples
bytes("Hello")
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...
capitalizeEveryWord(str: "well, hello there!") //Well, Hello There!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 True if the 2 given strings are perfect anagrams of each other, False if otherwise.
/// Return `true` if the 2 given strings are "perfect" anagrams.
/// (they consist of the same characters excluding whitespace)
func anagram(_ str1: String, _ str2: String) -> Bool {
let s1 = str1.filter { !$0.isWhitespace }.lowercased()
let s2 = str2.filter { !$0.isWhitespace }.lowercased()
return s1.count == s2.count && s1.sorted() == s2.sorted()
}View Examples
anagram("abcd3", "3acdb") // true
anagram("123", "456") // false
anagram("Buckethead", "Death Cube K") // trueReturns 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)Returns a CSV-String created from 2D-Array.
func arrayToCSV(_ inputArray: [Array<String>]) -> String {
var csv: String = ""
for row in inputArray {
csv.append(row.map { "\"\($0)\"" } .joined(separator: ", ") + "\n")
}
return csv
}View Examples
arrayToCSV([["a", "b", "c"], ["d", "e", "f"], ["g", "h", "i"]])
//"a", "b", "c"
//"d", "e", "f"
//"g", "h", "i"Returns the given function with fliped arguments.
func flip<A, B, C>(_ function: @escaping ((A, B) -> C)) -> ((B, A)->C) {
return { (a, b) in
return function(b, a)
}
}View Examples
// flip example 1
func concat(_ alpha: String, _ beta: String) -> String {
return alpha + beta
}
let reverseConcat = flip(concat)
concat("A", "B") //"AB"
reverseConcat("A", "B") //"BA"
// flip example 2
func gt(_ a: Int, _ b: Int) -> Bool {
return a > b
}
let lt = flip(gt)
gt(5, 3) //true
lt(5, 3) //false
gt(2, 5) //false
lt(2, 5) //trueRemoves elements from the end of an array until the passed function returns true.
func dropRight(arr: [Int], while predicate: ((Int) -> Bool)) -> [Int] {
var returnArr = arr
for item in arr.reversed() {
if predicate(item) { break }
returnArr = returnArr.dropLast()
}
return returnArr
}View Examples
dropRight(arr: [1, 2, 3, 4, 5], while: { $0 < 0 }) //[]
dropRight(arr: [1, 2, 3, 4, 5], while: { $0 > 0 }) //[1, 2, 3, 4, 5]Filters out the non-unique values in a list
func filterNonUnique(arr: [Any]) -> [Any] {
let set = NSOrderedSet(array: arr)
return set.array
}View Examples
filterNonUnique(arr: [1, 2, 2, 3, 5]) // [1, 2, 3, 5]
filterNonUnique(arr: ["Tim", "Steve", "Tim", "Jony", "Phil"]) // ["Tim", "Steve", "Jony", "Phil"]Returns a new string in snake case
func snake(str: String) -> String? {
let pattern = "([a-z0-9])([A-Z])"
let regex = try? NSRegularExpression(pattern: pattern, options: [])
let range = NSRange(location: 0, length: str.count)
return regex?.stringByReplacingMatches(in: str, options: [], range: range, withTemplate: "$1_$2")
.lowercased()
.replacingOccurrences(of: " ", with: "_")
.replacingOccurrences(of: "-", with: "_")
}View Examples
snake(str: "camelCase") // 'camel_case'
snake(str: "some text") // 'some_text'
snake(str: "some-mixed_string With spaces_underscores-and-hyphens") // 'some_mixed_string_with_spaces_underscores_and_hyphens'
snake(str: "AllThe-small Things") // "all_the_smal_things"Returns a new string in snake case
func snakeCase(_ string: String) -> String {
let arrayOfStrings = text.components(separatedBy: " ")
return arrayOfStrings.joined(separator: "_")
}View Examples
let text = "Snake case is the practice of writing compound words or phrases in which the elements are separated with one underscore character and no spaces."
snakeCase(text)Returns first unique character in a string
func firstUniqueCharacter(_ str: String) -> Character? {
var countDict: [Character: Int] = [:]
for char in str {
countDict[char] = (countDict[char] ?? 0) + 1
}
return str.filter{countDict[$0] == 1}.first
}View Examples
firstUniqueCharacter("barbeque nation") //"r"Prints a string N times without using loops.
func repeating(_ repeatedValue: String, count: Int) {
guard count > 0 else {
return
}
print(repeatedValue)
repeating(repeatedValue, count: count - 1)
}View Examples
repeating("Text", count: 5)Returns length of string in bytes
func stringLenghtInBytes(string: String) -> Int {
return (string as NSString).length
}View Examples
stringLenghtInBytes("Hello")
Returns every nth element from given list.
func everyNth(list: [Any], n: Int) -> [Any] {
return list.enumerated().compactMap({ ($0.offset + 1) % n == 0 ? $0.element : nil })
}View Examples
everyNth(list: [1, 2, 3, 4, 5, 6], n: 2) // [ 2, 4, 6 ]
everyNth(list: ["a", "b", "c", "d", "e", "f"], n: 3) // [ "c", "f" ]Returns 1 if array is sorted in ascending order, -1 if descending order, and 0 if unsorted
func isSorted(arr: [Int]) -> Int {
var asc: Bool = true
var prev: Int = Int.min
for elem in arr {
if elem < prev {
asc = false
break
}
prev = elem
}
if asc {
return 1
}
var dsc: Bool = true
prev = Int.max
for elem in arr {
if elem > prev {
dsc = false
break
}
prev = elem
}
if dsc {
return -1
}
return 0
}View Examples
isSorted(arr: [1, 2, 2, 4, 8]) // 1
isSorted(arr: [8, 4, 4, 2, 1]) // -1
isSorted(arr: [1, 4, 2, 8, 4]) // 0Returns 1 if array is sorted in ascending order, -1 if descending order, and 0 if unsorted - OPTION 2 shortest
func sortedArray (arr: [Int]) -> Int {
let sortedArr = arr.sorted(by: {$1>$0})
return arr == sortedArr ? 1 : arr == sortedArr.reversed() ? -1 : 0
}View Examples
//Input sortedArray(arr: [1,2,3,4,5]) - Output 1
//Input sortedArray(arr: [5,4,3,2,1]) - Output -1
//Input sortedArray(arr: [6,2,3,4,8]) - Output 0Convert camel case string (ex.'appleStore', 'TimCook') to snake case (ex. apple_store, 'tim_cook')
func camelCaseToSnake(str: String) -> String {
guard let regex = try? NSRegularExpression(pattern: "([a-z0-9])([A-Z])", options: []) else {
return str
}
let range = NSRange(location: 0, length: str.count)
return regex.stringByReplacingMatches(in: str, options: [], range: range, withTemplate: "$1_$2").lowercased()
}View Examples
camelCaseToSnake(str: "appleIphoneX")
camelCaseToSnake(str: "camelCaseStringToSnakeCase")
camelCaseToSnake(str: "string")
camelCaseToSnake(str: String())
camelCaseToSnake(str: "firstPullRequestForHacktoberFest🍁☔️🤖")Flip takes a function as an argument, then makes the first argument the last.
func flip<A,B,C>(_ f:@escaping (A,B) -> C) -> (B,A) -> C {
return { (b,a) in f(a,b) }
}View Examples
String.init(repeating:"🥳",count:5) == flip(String.init(repeating:count:))(5,"🥳") //trueReturns the neighbors of a vertex
public func neighborsForIndex(_ index: Int) -> [VertexType] {
return edges[index].map({self.vertices[$0.v]})
}