I'm trying to calculate the number of times a specific number is rolled in a set of six six-sided dice, to determine wether or not I have three of a kind, four of a kind, etc.
I can pull the face value of each die rolled and compare it to the faces on a 6 sided die but can't get the "qtyRolled" key/value to increment.
func rollDice() {
currentRoll.removeAll()
for _ in currentDiceArray {
let num: UInt32 = arc4random_uniform(UInt32(currentDieFaceArray.count))
let currentDieData = currentDieFaceArray[Int(num)]
let faceValue = currentDieData["faceValue"]
currentRoll.append(faceValue as! Int)
}
print(currentRoll)
getQtyOfDieFaces()
//checkForScoringCombos()
}
func getQtyOfDieFaces() {
for die in currentRoll {
for dieData in currentDieFaceArray {
var currentDieData = dieData
let qtyRolled = currentDieData["qtyRolled"] as! Int
let faceValue = currentDieData["faceValue"] as! Int
print("faceValue: \(faceValue)")
print("Die: \(die)")
if faceValue == die {
currentDieData["qtyRolled"] = qtyRolled + 1 as AnyObject
}
}
}
for currentDieData in currentDieFaceArray {
print(currentDieData["qtyRolled"]!)
}
}
Here are my data structures
var currentDieFaceArray = [[String:AnyObject]]()
var currentDiceArray:[[String:AnyObject]] = [[:]]
var currentRoll: [Int] = []
I'd recommend ditching the dictionaries unless you really need them, as you're really just dealing with properties of a struct/class. I'm going to assume you're using the currentDieFaceArray method so that you can make this generic for non-linear dice faces of other dimensions (e.g. you can have a four-sided dice with the face values [1, 4, 6, 8]). If this isn't the case, you can simplify further I'm sure with a simple array of counts. But here's an example with your method (probably has other possible optimisations).
class DieFaceDefn
{
let faceValue : Int
var countThisRoll : Int = 0
init(faceValue: Int)
{
self.faceValue = faceValue
}
}
var diceFaces: [DieFaceDefn] = []
let numberOfCurrentDice = 5
func setupDice()
{
diceFaces.append(DieFaceDefn(faceValue: 1))
diceFaces.append(DieFaceDefn(faceValue: 2))
...
}
var currentRoll: [Int] = []
func rollDice()
{
currentRoll.removeAll()
diceFaces.forEach { $0.countThisRoll = 0 }
for _ in 0..<numberOfCurrentDice
{
let num: UInt32 = arc4random_uniform(UInt32(diceFaces.count))
let currentDieData = diceFaces[Int(num)]
let faceValue = currentDieData.faceValue
currentRoll.append(faceValue)
currentDieData.countThisRoll += 1
}
print(currentRoll)
diceFaces.forEach { print("\($0.faceValue): \($0.countThisRoll)") }
}
One can filter an array like this in swift:
var numbers = Array(1...1000000)
numbers = numbers.filter( { return $0 % 2 == 0 } )
Is it possible to filter and avoid the copy operation, that occurs when the filtering is done, e.g mutating the original array.
In a similar way to this pseudocode:
numbers.MutablefilterOperation({ return $0 % 2 == 0})
In C++ the equvivalent to what is going on in Swift above would be:
std::vector<int> originalNumbers(1000000);
std::vector<int> newNumbers;
std::copy_if (originalNumbers.begin(), originalNumbers.end(), std::back_inserter(newNumbers), [](int i) { return i % 2 == 0 } );
What I would like to achieve for performance reasons:
std::vector<int> originalNumbers(1000000);
auto pos = std::remove_if(originalNumbers.begin(), originalNumbers.end(), [](int x) { return x % 2 == 0; });
originalNumbers.erase(pos, originalNumbers.end());
This implementation should do the filtering without having to make a temporary copy of the entire array in the process (unless a copy of it is referenced by another variable, see "Copy on Write")
extension Array {
mutating func filterInPlace(isIncluded: (Element) throws -> Bool) rethrows {
var writeIndex = self.startIndex
for readIndex in self.indices {
let element = self[readIndex]
let include = try isIncluded(element)
if include {
if writeIndex != readIndex {
self[writeIndex] = element
}
writeIndex = self.index(after: writeIndex)
}
}
self.removeLast(self.distance(from: writeIndex, to: self.endIndex))
}
}
// example:
var arr = [6,2,6,5,2,5,6,2,2,1,6,7,3]
arr.filterInPlace { $0 % 2 == 1 }
print(arr) // [5, 5, 1, 7, 3]
Here is my code, inside of my for loop, there is a while loop changes
the variable i's value. I printed out the value of i before while loop
and and after loop, the new "before index value" is expected to start
at "after index value +1". However, the "new before index value" just
increase as normal, which increase one each time. Appreciate your time.
class Solution
{
func summaryRange(nums: [Int]) -> [String]
{
var result = [String]()
if nums.count == 1
{
result.append(String(nums[0])+"")
return result
}
for var i in (0...nums.count-1)
{
let a = nums[i]
print("before: \(i)")
while i+1<nums.count && (nums[i+1] - nums[i] == 1)
{
i += 1
}
if a != nums[i]
{
result.append(String(a) + "->" + String(nums[i]))
}
else
{
result.append(String(a)+"")
}
print("after: \(i)")
}
return result
}
}
var test = Solution()
var input = [0,1,2,4,5,7]
var result = test.summaryRange(input)
print(result)
This code tries to get result like ["0->2","4->5","7"]
This is my own solution. I figure out the problem. Basically, I switch
the "for loop" to a "while loop". Then, it works.
class Solution
{
func summaryRanges(nums: [Int]) -> [String]
{
var result = [String]()
var i = 0
while(i<nums.count)
{
let a = nums[i]
while i+1<nums.count && (nums[i+1] - nums[i] == 1)
{
i += 1
}
if a != nums[i]
{
result.append(String(a) + "->" + String(nums[i]))
}
else
{
result.append(String(a)+"")
}
i += 1
}
return result
}
}
In swift, for in loop is a wrapper around the Sequence Type. In this particular case, 0...numCount-1 is a Sequence of Ints. When you call for in this is what happens internally.
let a = 0..<5
var generator = a.generate()
while var i = generator.next() {
print(i + 1)
i+= 1
}
So even if you increment the value of i inside the loop, it wont affect the loop itself. This is because loop is controller only by calling genertator.next().
This helps understand the basics.
This was an interesting one. I think this does the trick (with some code cleanup as well :-]
class Solution
{
func summaryRange(nums: [Int]) -> [String] {
var result = [String]()
var currentRange = [Int]()
for num in nums {
if currentRange.isEmpty { //if range is empty, start a new range
currentRange.append(num)
continue
}
if num - 1 != currentRange.last! { //if not next number in sequence, close range, start new
result.append(closeRange(currentRange))
currentRange = []
currentRange.append(num)
} else if num - 1 == currentRange.last {
currentRange.append(num) //if next number, add to range
}
}
if !currentRange.isEmpty {
result.append(closeRange(currentRange)) //check for unclosed ranges
}
return result
}
func closeRange(range: [Int]) -> String {
guard range.count > 0 else { return "" }
if range.count == 1 { return String(range.first!) }
return "\(range.first!)->\(range.last!)"
}
}
var test = Solution()
var input = [0,1,2,4,5,7]
var result = test.summaryRange(input)
print(result)
Let me know how this works for you!
struct Home {
var street:String
var number:Int
}
func getHouse() -> [Home] {
var house = [Home]()
let house1 = Home(street: "Jacob Street", number: 26)
house.append(house1)
let house2 = Home(street: "High Road", number: 58)
house.append(house2)
let house3 = Home(street: "Zebra Close", number: 12)
house.append(house3)
return house
}
var houses = [Home]()
houses = getHouse()
houses.sort({$0.street < $1.street })
for i in 0..<houses.count {
print("\(houses[i].street)")
}
I'm trying to sort them alphabetically by street in this example, or possibly by number if needed. They still seem to stay in the order I've put them in rather than being in alphabetical order which i want.
The sort returns a new array, but you're not doing anything with the result. You can either do
let sortedHouses = houses.sort {$0.street < $1.street }
or
houses.sortInPlace {$0.street < $1.street }
You might use sortInPlace(),
sort() returns a new sorted object and leaves the receiver unchanged.
Or
let sortedHouses = houses.sort {$0.street < $1.street }
Suppose I have an array and I want to pick one element at random.
What would be the simplest way to do this?
The obvious way would be array[random index]. But perhaps there is something like ruby's array.sample? Or if not could such a method be created by using an extension?
Swift 4.2 and above
The new recommended approach is a built-in method on the Collection protocol: randomElement(). It returns an optional to avoid the empty case I assumed against previously.
let array = ["Frodo", "Samwise", "Merry", "Pippin"]
print(array.randomElement()!) // Using ! knowing I have array.count > 0
If you don't create the array and aren't guaranteed count > 0, you should do something like:
if let randomElement = array.randomElement() {
print(randomElement)
}
Swift 4.1 and below
Just to answer your question, you can do this to achieve random array selection:
let array = ["Frodo", "Samwise", "Merry", "Pippin"]
let randomIndex = Int(arc4random_uniform(UInt32(array.count)))
print(array[randomIndex])
The castings are ugly, but I believe they're required unless someone else has another way.
Riffing on what Lucas said, you could create an extension to the Array class like this:
extension Array {
func randomItem() -> Element? {
if isEmpty { return nil }
let index = Int(arc4random_uniform(UInt32(self.count)))
return self[index]
}
}
For example:
let myArray = [1, 2, 3, 4, 5, 6, 7, 8, 10, 12, 14, 16]
let myItem = myArray.randomItem() // Note: myItem is an Optional<Int>
Swift 4 version:
extension Collection where Index == Int {
/**
Picks a random element of the collection.
- returns: A random element of the collection.
*/
func randomElement() -> Iterator.Element? {
return isEmpty ? nil : self[Int(arc4random_uniform(UInt32(endIndex)))]
}
}
In Swift 2.2 this can be generalised so that we have:
UInt.random
UInt8.random
UInt16.random
UInt32.random
UInt64.random
UIntMax.random
// closed intervals:
(-3...3).random
(Int.min...Int.max).random
// and collections, which return optionals since they can be empty:
(1..<4).sample
[1,2,3].sample
"abc".characters.sample
["a": 1, "b": 2, "c": 3].sample
First, implementing static random property for UnsignedIntegerTypes:
import Darwin
func sizeof <T> (_: () -> T) -> Int { // sizeof return type without calling
return sizeof(T.self)
}
let ARC4Foot: Int = sizeof(arc4random)
extension UnsignedIntegerType {
static var max: Self { // sadly `max` is not required by the protocol
return ~0
}
static var random: Self {
let foot = sizeof(Self)
guard foot > ARC4Foot else {
return numericCast(arc4random() & numericCast(max))
}
var r = UIntMax(arc4random())
for i in 1..<(foot / ARC4Foot) {
r |= UIntMax(arc4random()) << UIntMax(8 * ARC4Foot * i)
}
return numericCast(r)
}
}
Then, for ClosedIntervals with UnsignedIntegerType bounds:
extension ClosedInterval where Bound : UnsignedIntegerType {
var random: Bound {
guard start > 0 || end < Bound.max else { return Bound.random }
return start + (Bound.random % (end - start + 1))
}
}
Then (a little more involved), for ClosedIntervals with SignedIntegerType bounds (using helper methods described further below):
extension ClosedInterval where Bound : SignedIntegerType {
var random: Bound {
let foot = sizeof(Bound)
let distance = start.unsignedDistanceTo(end)
guard foot > 4 else { // optimisation: use UInt32.random if sufficient
let off: UInt32
if distance < numericCast(UInt32.max) {
off = UInt32.random % numericCast(distance + 1)
} else {
off = UInt32.random
}
return numericCast(start.toIntMax() + numericCast(off))
}
guard distance < UIntMax.max else {
return numericCast(IntMax(bitPattern: UIntMax.random))
}
let off = UIntMax.random % (distance + 1)
let x = (off + start.unsignedDistanceFromMin).plusMinIntMax
return numericCast(x)
}
}
... where unsignedDistanceTo, unsignedDistanceFromMin and plusMinIntMax helper methods can be implemented as follows:
extension SignedIntegerType {
func unsignedDistanceTo(other: Self) -> UIntMax {
let _self = self.toIntMax()
let other = other.toIntMax()
let (start, end) = _self < other ? (_self, other) : (other, _self)
if start == IntMax.min && end == IntMax.max {
return UIntMax.max
}
if start < 0 && end >= 0 {
let s = start == IntMax.min ? UIntMax(Int.max) + 1 : UIntMax(-start)
return s + UIntMax(end)
}
return UIntMax(end - start)
}
var unsignedDistanceFromMin: UIntMax {
return IntMax.min.unsignedDistanceTo(self.toIntMax())
}
}
extension UIntMax {
var plusMinIntMax: IntMax {
if self > UIntMax(IntMax.max) { return IntMax(self - UIntMax(IntMax.max) - 1) }
else { return IntMax.min + IntMax(self) }
}
}
Finally, for all collections where Index.Distance == Int:
extension CollectionType where Index.Distance == Int {
var sample: Generator.Element? {
if isEmpty { return nil }
let end = UInt(count) - 1
let add = (0...end).random
let idx = startIndex.advancedBy(Int(add))
return self[idx]
}
}
... which can be optimised a little for integer Ranges:
extension Range where Element : SignedIntegerType {
var sample: Element? {
guard startIndex < endIndex else { return nil }
let i: ClosedInterval = startIndex...endIndex.predecessor()
return i.random
}
}
extension Range where Element : UnsignedIntegerType {
var sample: Element? {
guard startIndex < endIndex else { return nil }
let i: ClosedInterval = startIndex...endIndex.predecessor()
return i.random
}
}
You can use Swift's built-in random() function as well for the extension:
extension Array {
func sample() -> Element {
let randomIndex = Int(rand()) % count
return self[randomIndex]
}
}
let array = [1, 2, 3, 4]
array.sample() // 2
array.sample() // 2
array.sample() // 3
array.sample() // 3
array.sample() // 1
array.sample() // 1
array.sample() // 3
array.sample() // 1
Another Swift 3 suggestion
private extension Array {
var randomElement: Element {
let index = Int(arc4random_uniform(UInt32(count)))
return self[index]
}
}
Following others answer but with Swift 2 support.
Swift 1.x
extension Array {
func sample() -> T {
let index = Int(arc4random_uniform(UInt32(self.count)))
return self[index]
}
}
Swift 2.x
extension Array {
func sample() -> Element {
let index = Int(arc4random_uniform(UInt32(self.count)))
return self[index]
}
}
E.g.:
let arr = [2, 3, 5, 7, 9, 11, 13, 17, 19, 23, 29, 31]
let randomSample = arr.sample()
An alternative functional implementation with check for empty array.
func randomArrayItem<T>(array: [T]) -> T? {
if array.isEmpty { return nil }
let randomIndex = Int(arc4random_uniform(UInt32(array.count)))
return array[randomIndex]
}
randomArrayItem([1,2,3])
Here's an extension on Arrays with an empty array check for more safety:
extension Array {
func sample() -> Element? {
if self.isEmpty { return nil }
let randomInt = Int(arc4random_uniform(UInt32(self.count)))
return self[randomInt]
}
}
You can use it as simple as this:
let digits = Array(0...9)
digits.sample() // => 6
If you prefer a Framework that also has some more handy features then checkout HandySwift. You can add it to your project via Carthage then use it exactly like in the example above:
import HandySwift
let digits = Array(0...9)
digits.sample() // => 8
Additionally it also includes an option to get multiple random elements at once:
digits.sample(size: 3) // => [8, 0, 7]
Swift 3
import GameKit
func getRandomMessage() -> String {
let messages = ["one", "two", "three"]
let randomNumber = GKRandomSource.sharedRandom().nextInt(upperBound: messages.count)
return messages[randomNumber].description
}
Swift 3 - simple easy to use.
Create Array
var arrayOfColors = [UIColor.red, UIColor.yellow, UIColor.orange, UIColor.green]
Create Random Color
let randomColor = arc4random() % UInt32(arrayOfColors.count)
Set that color to your object
your item = arrayOfColors[Int(randomColor)]
Here is an example from a SpriteKit project updating a SKLabelNode with a random String:
let array = ["one","two","three","four","five"]
let randomNumber = arc4random() % UInt32(array.count)
let labelNode = SKLabelNode(text: array[Int(randomNumber)])
If you want to be able to get more than one random element out of your array with no duplicates, GameplayKit has you covered:
import GameplayKit
let array = ["one", "two", "three", "four"]
let shuffled = GKMersenneTwisterRandomSource.sharedRandom().arrayByShufflingObjects(in: array)
let firstRandom = shuffled[0]
let secondRandom = shuffled[1]
You have a couple choices for randomness, see GKRandomSource:
The GKARC4RandomSource class uses an algorithm similar to that employed in arc4random family of C functions. (However, instances of this class are independent from calls to the arc4random functions.)
The GKLinearCongruentialRandomSource class uses an algorithm that is faster, but less random, than the GKARC4RandomSource class. (Specifically, the low bits of generated numbers repeat more often than the high bits.) Use this source when performance is more important than robust unpredictability.
The GKMersenneTwisterRandomSource class uses an algorithm that is slower, but more random, than the GKARC4RandomSource class. Use this source when it’s important that your use of random numbers not show repeating patterns and performance is of less concern.
I find using GameKit's GKRandomSource.sharedRandom() works best for me.
import GameKit
let array = ["random1", "random2", "random3"]
func getRandomIndex() -> Int {
let randomNumber = GKRandomSource.sharedRandom().nextIntWithUpperBound(array.count)
return randomNumber
or you could return the object at the random index selected. Make sure the function returns a String first, and then return the index of the array.
return array[randomNumber]
Short and to the point.
There is a built-in method on Collection now:
let foods = ["🍕", "🍔", "🍣", "🍝"]
let myDinner = foods.randomElement()
If you want to extract up to n random elements from a collection you can add an extension like this one:
extension Collection {
func randomElements(_ count: Int) -> [Element] {
var shuffledIterator = shuffled().makeIterator()
return (0..<count).compactMap { _ in shuffledIterator.next() }
}
}
And if you want them to be unique you can use a Set, but the elements of the collection must conform to the Hashable protocol:
extension Collection where Element: Hashable {
func randomUniqueElements(_ count: Int) -> [Element] {
var shuffledIterator = Set(shuffled()).makeIterator()
return (0..<count).compactMap { _ in shuffledIterator.next() }
}
}
Latest swift3 code try it its working fine
let imagesArray = ["image1.png","image2.png","image3.png","image4.png"]
var randomNum: UInt32 = 0
randomNum = arc4random_uniform(UInt32(imagesArray.count))
wheelBackgroundImageView.image = UIImage(named: imagesArray[Int(randomNum)])
I figured out a very different way to do so using the new features introduced in Swift 4.2.
// 👇🏼 - 1
public func shufflePrintArray(ArrayOfStrings: [String]) -> String {
// - 2
let strings = ArrayOfStrings
//- 3
var stringans = strings.shuffled()
// - 4
var countS = Int.random(in: 0..<strings.count)
// - 5
return stringans[countS]
}
we declared a function with parameters taking an array of Strings and returning a String.
Then we take the ArrayOfStrings in a variable.
Then we call the shuffled function and store that in a variable. (Only supported in 4.2)
Then we declare a variable which saves a shuffled value of total count of the String.
Lastly we return the shuffled string at the index value of countS.
It is basically shuffling the array of strings and then also have a random pick of number of the total number of count and then returning the random index of the shuffled array.