Like: 0123, 0913, 7612
Not like: 0000, 1333, 3499
Can it be done with arcRandom() in swift? Without array or loop?
Or If that impossible, how it be done with arcRandom() in any way ?
You just want to shuffle the digits and pick the number you want.
Start with Nate Cook's Fischer-Yates shuffle code.
// Start with the digits
let digits = 0...9
// Shuffle them
let shuffledDigits = digits.shuffle()
// Take the number of digits you would like
let fourDigits = shuffledDigits.prefix(4)
// Add them up with place values
let value = fourDigits.reduce(0) {
$0*10 + $1
}
var fourUniqueDigits: String {
var result = ""
repeat {
// create a string with up to 4 leading zeros with a random number 0...9999
result = String(format:"%04d", arc4random_uniform(10000) )
// generate another random number if the set of characters count is less than four
} while Set<Character>(result.characters).count < 4
return result // ran 5 times
}
fourUniqueDigits // "3501"
fourUniqueDigits // "8095"
fourUniqueDigits // "9054"
fourUniqueDigits // "4728"
fourUniqueDigits // "0856"
Swift Code - For Generation of 4 digit
It gives number between 1000 and 9999.
func random() -> String {
var result = ""
repeat {
result = String(format:"%04d", arc4random_uniform(10000) )
} while result.count < 4 || Int(result)! < 1000
print(result)
return result
}
Please Note - You can remove this Int(result)! < 1000 if you want numbers like this - 0123, 0913
Related
Eg:
HelloWorld - repeated characters are 5 (l is repeating 3 times and o is repeating 2 times)
Smart2000, repeated characters = 3?(0 is repeating 3 times)
Smart#200#12, repeated characters = 6
I tried with iterating over string
Here is my code with string iteration to find out the repeated character in string.
func countRepeatDigitsIn(keyword : String) -> Int
{
// To keep track of processed symbols
var uniqueCharacters = ""
var repeatCharacterCount = 0
for char in keyword.uppercased() {
let alphabet = String(char)
// If this is already counted, skip it
if (uniqueCharacters.contains(alphabet))
{
repeatCharacterCount += 1
}
// Otherwise, add it to processed symbols
uniqueCharacters += alphabet
}
return repeatCharacterCount
}
HelloWorld - repeated characters are 5 (l is repeating 3 times and o is repeating 2 times
The simplest way to get that result is to take a histogram and then add up all the values that are not 1.
Example:
func histogram(_ s:String) -> [Character:Int] {
var d = [Character:Int]()
for c in s {
d[c, default:0] += 1
}
return d
}
let reps = histogram("helloworld").values.filter{$0 > 1}.reduce(0, +) // 5
let reps2 = histogram("smart2000").values.filter{$0 > 1}.reduce(0, +) // 3
let reps3 = histogram("Smart#200#12").values.filter{$0 > 1}.reduce(0, +) // 6
Here's a fun chain of reductions and filters on the characters of the string.
func countRepeatDigitsIn(keyword : String) -> Int {
let total = Array(keyword.uppercased()).reduce(into: [Character : Int]()) { $0[$1, default: 0] += 1 }.filter { $0.value > 1 }.reduce(0) { $0 + $1.value }
return total
}
for text in ["HelloWorld", "Smart2000", "Smart#200#12"] {
print(text, countRepeatDigitsIn(keyword: text))
}
The first reduce builds a dictionary where the keys are characters and the values is the count for the character. Then the filter removes characters only found once. The second reduce adds the remaining counts.
Group same characters in a dictionary using Dictionary(grouping:by:) and add the counts of values where the count is greater than 1
extension String {
func repeatCount() -> Int {
return Dictionary(grouping: lowercased()) { $0 }.values.filter { $0.count > 1 }.reduce(0) { $0 + $1.count }
}
}
print("HelloWorLd".repeatCount())//5
print("Smart2000".repeatCount())//3
print("Smart#200#12".repeatCount())//6
I'm attempting to get a user input number and find the sum of all the digits. I'm having issues with larger numbers, however, as they won't register under an Int64. Any idea as to what structures I could use to store the value? (I tried UInt64 and that didn't work very well with negatives, however, I'd prefer something larger than UInt64, anyways. I'm having a hard time implementing a UInt128 from Is there a number type with bigger capacity than u_long/UInt64 in Swift?)
import Foundation
func getInteger() -> Int64 {
var value:Int64 = 0
while true {
//we aren't doing anything with input, so we make it a constant
let input = readLine()
//ensure its not nil
if let unwrappedInput = input {
if let unwrappedInt = Int64(unwrappedInput) {
value = unwrappedInt
break
}
}
else { print("You entered a nil. Try again:") }
}
return value
}
print("Please enter an integer")
// Gets user input
var input = getInteger()
var arr = [Int] ()
var sum = 0
var negative = false
// If input is less than 0, makes it positive
if input < 0 {
input = (input * -1)
negative = true
}
if (input < 10) && (input >= 1) && (negative == true) {
var remain = (-1)*(input%10)
arr.append(Int(remain))
input = (input/10)
}
else {
var remain = (input%10)
arr.append(Int(remain))
input = (input/10)
}
}
// Adds numbers in array to find sum of digits
var i:Int = 0
var size:Int = (arr.count - 1)
while i<=size {
sum = sum + arr[i]
i = (i+1)
}
// Prints sum
print("\(sum)")
You can use a string to perform the operation you describe. Loop through each character and convert it to an integer and add to the sum. Be careful to handle errors.
This code picks a random color from a array of pre-set colors. How do I make it so the same color doesn't get picked more than once?
var colorArray = [(UIColor.redColor(), "red"), (UIColor.greenColor(), "green"), (UIColor.blueColor(), "blue"), (UIColor.yellowColor(), "yellow"), (UIColor.orangeColor(), "orange"), (UIColor.lightGrayColor(), "grey")]
var random = { () -> Int in
return Int(arc4random_uniform(UInt32(colorArray.count)))
} // makes random number, you can make it more reusable
var (sourceColor, sourceName) = (colorArray[random()])
Create an array of indexes. Remove one of the indexes from the array and then use that to fetch a color.
Something like this:
var colorArray = [
(UIColor.redColor(), "red"),
(UIColor.greenColor(), "green"),
(UIColor.blueColor(), "blue"),
(UIColor.yellowColor(), "yellow"),
(UIColor.orangeColor(), "orange"),
(UIColor.lightGrayColor(), "grey")]
var indexes = [Int]();
func randomItem() -> UIColor
{
if indexes.count == 0
{
print("Filling indexes array")
indexes = Array(0..< colorArray.count)
}
let randomIndex = Int(arc4random_uniform(UInt32(indexes.count)))
let anIndex = indexes.removeAtIndex(randomIndex)
return colorArray[anIndex].0;
}
The code above creates an array indexes. The function randomItem looks to see if indexes is empty. if it is, it populates it with index values ranging from 0 to colorArray.count - 1.
It then picks a random index in the indexes array, removes the value at that index in the indexes array, and uses it to fetch and return an object from your colorArray. (It doesn't remove objects from the colorArray. It uses indirection, and removes objects from the indexesArray, which initially contains an index value for each entry in your colorArray.
The one flaw in the above is that after you fetch the last item from indexArray, you populate it with a full set of indexes, and it's possible that the next color you get from the newly repopulated array will be the same as the last one you got.
It's possible to add extra logic to prevent this.
based on the fact, that arc4random_uniform generate not only random, but also uniformly distributed numbers
import Foundation // arc4random_uniform
class Random {
var r:UInt32
let max: UInt32
init(max: UInt32) {
self.max = max
r = arc4random_uniform(max)
}
var next: UInt32 {
var ret: UInt32
repeat {
ret = arc4random_uniform(max)
} while r == ret
r = ret
return r
}
}
// usage example
let r = Random(max: 5)
for i in 0..<10 {
print(r.r, r.next) // there will never be a pair of the same numbers in the
// generated stream
}
/*
2 4
4 0
0 3
3 0
0 3
3 4
4 1
1 3
3 4
4 3
*/
simple test for different k and stream length of one milion
class Random {
var r:UInt32
let max: UInt32
init(max: UInt32) {
self.max = max
r = arc4random_uniform(max)
}
var next: (UInt32, Int) {
var i = 0
var ret: UInt32
repeat {
ret = arc4random_uniform(max)
i += 1
} while r == ret
r = ret
return (r,i)
}
}
for k in 3..<16 {
let r = Random(max: UInt32(k))
var repetition = 0
var sum = 0
for i in 0..<1000000 {
let j = r.next
repetition = max(repetition, j.1)
sum += j.1
}
print("maximum of while repetition for k:", k, "is", repetition, "with average of", Double(sum) / Double(1000000) )
}
prints
maximum of while repetition for k: 3 is 15 with average of 1.499832
maximum of while repetition for k: 4 is 12 with average of 1.334008
maximum of while repetition for k: 5 is 9 with average of 1.250487
maximum of while repetition for k: 6 is 8 with average of 1.199631
maximum of while repetition for k: 7 is 8 with average of 1.167501
maximum of while repetition for k: 8 is 7 with average of 1.142799
maximum of while repetition for k: 9 is 8 with average of 1.124096
maximum of while repetition for k: 10 is 6 with average of 1.111178
maximum of while repetition for k: 11 is 7 with average of 1.099815
maximum of while repetition for k: 12 is 7 with average of 1.091041
maximum of while repetition for k: 13 is 6 with average of 1.083582
maximum of while repetition for k: 14 is 6 with average of 1.076595
maximum of while repetition for k: 15 is 6 with average of 1.071965
finaly, here is more Swifty and functional approach based on the same idea
import Foundation
func random(max: Int)->()->Int {
let max = UInt32(max)
var last = arc4random_uniform(max)
return {
var r = arc4random_uniform(max)
while r == last {
r = arc4random_uniform(max)
}
last = r
return Int(last)
}
}
let r0 = random(8)
let r1 = random(4)
for i in 0..<20 {
print(r0(), terminator: " ")
}
print("")
for i in 0..<20 {
print(r1(), terminator: " ")
}
/*
4 5 4 3 4 0 5 6 7 3 6 7 5 4 7 4 7 2 1 6
0 3 0 1 0 2 3 1 2 0 1 0 1 0 1 3 0 3 0 2
*/
Fill an array with the colors and shuffle it with a Fisher-Yates shuffle. Then use the element at an end, remove it, and insert it at a random position at least n positions from the end.
For example, say my array has 10 elements. I shuffle it and take the last. I want at least 2 values to be chosen before I see it again so I generate a random position in the range 0...8 and insert it there.
var colorArray = [
(UIColor.redColor() , "red" ),
(UIColor.greenColor() , "green" ),
(UIColor.blueColor() , "blue" ),
(UIColor.yellowColor() , "yellow"),
(UIColor.orangeColor() , "orange"),
(UIColor.lightGrayColor(), "grey" )].shuffle() // shuffle() is from my link above
let spacing = 2 // Pick at least 2 colors before we see it again
if let randomColor = colorArray.popLast() {
colorArray.insert(randomColor,
atIndex: Int(arc4random_uniform(UInt32(colorArray.count - spacing))))
}
One case, described here: https://github.com/dimpiax/GenericSequenceType
Another is functional:
func getRandomItem<T>(arr: [T]) -> (unique: Bool) -> T {
var indexes: [Int]!
return { value in
let uniqIndex: Int
if value {
if indexes?.isEmpty != false {
indexes = [Int](0.stride(to: arr.count, by: 1))
}
uniqIndex = indexes.removeAtIndex(Int(arc4random_uniform(UInt32(indexes.count))))
}
else {
uniqIndex = Int(arc4random_uniform(UInt32(arr.count)))
}
return arr[uniqIndex]
}
}
let generate = getRandomItem(colorArray)
generate(unique: true).0 // greenColor
generate(unique: true).0 // redColor
generate(unique: true).0 // lightGrayColor
Try it it's work for me and 100% tested
let arrString = ["1","2","3","4","5","6"]
var selectedIndix = -1
#IBAction func btnClick(_ sender: Any) {
let randomElementIndex = randomElementString()
}
Call this function when button clicked
func randomElementString() -> Int{
let randomm = Int(arc4random_uniform(UInt32(arrString.count)))
if selectedIndix == randomm{
return randomElementString()
}else{
selectedIndix = randomm
return randomm
}
}
OUTPUT:-
5121242316513126
How about running a while loop with the condition:
while(self.source.backgroundColor == sourceColor) {
// get a new random sourceColor
}
This will keep looping until a new random color has been selected.
edit
Additional Note: The point was the while loop. There are ways to safeguard from an infinite loop, it's up to the coder to find the right solution. I don't think SO is a place to write other's code but instead to offer suggestions .. mine is a start.
But since my answer was given such a negative rating, i'll push instead of nudge in the right direction.
The other answers are unnecessarily bloated. And? The one I offered above offers a less than desirable time complexity. So, here's my new answer (in meta code):
// array of all background colors
var arrayOfColors = [..]
// get a random index
var randomIndex = arc4random(size of arrayOfColors)
// select new background color
var newBGColor = arrayOfColors[randomIndex]
// old background color
var oldBGColor = self.source.backgroundColor
// remove new color from array (so that it's excluded from choices next time)
arrayOfColors.removeAtIndex(randomIndex)
// set the new color to the background
self.source.backgroundColor = newBGColor
// add current color back into the pool of potential colors
arrayOfColors.addObject(oldBGColor)
I'm working on a project which includes verifying the checksum of an Int input with the Damm Algorithm. I've managed to create a the operational table and my method for accessing the value in the table involves passing an interim value and a digit to pass in as the column value.
ex.
self.tableToUse[interim,checkSumArray[i]]
Unfortunately, I've run into a snag when I'm trying to pass the digits from my input into the the get/set method where I cannot find a way to convert the Characters into Ints.
func encode(number: Int) -> Int{
var checkSumArray = [Int]()
if number > 99999999 {
println("number is too large")
return 0
}
else if number < 0 {
println("invalid input")
return 0
}
else {
checkSumArray.append(number%(10))
checkSumArray.append((number%(100)-checkSumArray[0])/10)
checkSumArray.append((number%(1000)-checkSumArray[1])/100)
checkSumArray.append((number%(10000)-checkSumArray[2])/1000)
checkSumArray.append((number%(100000)-checkSumArray[3])/10000)
checkSumArray.append((number%(1000000)-checkSumArray[4])/100000)
checkSumArray.append((number%(10000000)-checkSumArray[5])/1000000)
checkSumArray.append((number%(100000000)-checkSumArray[6])/10000000)
checkSumArray = checkSumArray.reverse()
var interim: Int = 0
for i in 0..<checkSumArray.count{
interim = self.tableToUse[interim,checkSumArray[i]]
}
return interim
}
}
As you can see, I've had to resort to a really nasty way of dealing with this. It works, but it's very limited, inefficient, and just ugly to look at or maintain. I've looked at the option of using Characters instead of Ints in the Damm Table I've constructed and altering the get/set method to deal with those instead, but that's a lot of extra work and could introduce other issues. Any suggestions of alternative ways to handle this, or a way to convert Characters to Ints would be appreciated.
Thanks!
Based on How convert a *positive* number into an array of digits in Swift, you could do (the number has to be positive):
let checkSumArray = map(number.description) { String($0).toInt()! }
if let int = Int(String(Character("1"))) {
print(int)
}
You can also create a character extension as follow:
extension Character {
var integerValue: Int? {
return Int(String(self))
}
}
Testing
Character("1").integerValue // 1
Character("2").integerValue // 2
Character("3").integerValue // 3
Character("4").integerValue // 4
Character("5").integerValue // 5
Character("6").integerValue // 6
Character("7").integerValue // 7
Character("8").integerValue // 8
Character("9").integerValue // 9
Character("0").integerValue // 0
Character("a").integerValue // nil
Array("9876").first!.integerValue // 9
Array("9876")[1].integerValue // 8
Array("9876")[2].integerValue // 7
Array("9876").last!.integerValue // 6
edit/update Swift 5
Swift 5 adds many new properties to the Character and one of them fits exactly to this purpose. It is called wholeNumberValue
Character("1").wholeNumberValue // 1
Character("2").wholeNumberValue // 2
Character("3").wholeNumberValue // 3
Character("4").wholeNumberValue // 4
Character("④").wholeNumberValue // 4
Character("5").wholeNumberValue // 5
Character("6").wholeNumberValue // 6
Character("7").wholeNumberValue // 7
Character("8").wholeNumberValue // 8
Character("9").wholeNumberValue // 9
Character("0").wholeNumberValue // 0
Character("万").wholeNumberValue // 10_000
Character("a").wholeNumberValue // nil
There is no need to work with characters, but your code to create an
array with the decimal digits of the input number can be greatly
simplified:
var checkSumArray = [Int]()
var tmp = number
while tmp > 0 {
checkSumArray.append(tmp % 10)
tmp /= 10
}
checkSumArray = checkSumArray.reverse()
I'd like to generate multiple different random numbers in Swift. Here is the procedure.
Set up an empty array
Generate a random number
Check if the array is empty
a. If the array is empty, insert the random number
b. If the array is not empty, compare the random number to the numbers in array
i. If the numbers are the same, repeat 2
ii. if the numbers are not the same, insert the random number and repeat 2
import UIKit
//the random number generator
func randomInt(min: Int, max:Int) -> Int {
return min + Int(arc4random_uniform(UInt32(max - min + 1)))
}
var temp = [Int]()
for var i = 0; i<4; i++ {
var randomNumber = randomInt(1, 5)
if temp.isEmpty{
temp.append(randomNumber)
} else {
//I don't know how to continue...
}
}
If you use your method the problem is, that you will create a new random-number each time. So you possibly could have the same random-number 4 times and so your array will only have one element.
So, if you just want to have an array of numbers from within a specific range of numbers (for example 0-100), in a random order, you can first fill an array with numbers in 'normal' order. For example with for loop etc:
var min = 1
var max = 5
for var i = min; i<= max; i++ {
temp.append(i)
}
After that, you can use a shuffle method to shuffle all elements of the array with the shuffle method from this answer:
func shuffle<C: MutableCollectionType where C.Index == Int>(var list: C) -> C {
let count = countElements(list)
for i in 0..<(count - 1) {
let j = Int(arc4random_uniform(UInt32(count - i))) + i
swap(&list[i], &list[j])
}
return list
}
Ater that you can do something like that:
shuffle(temp) // e.g., [3, 1, 2, 4, 5]
The construct you’re looking for with your approach might be something like:
var temp: [Int] = []
while temp.count < 4 {
var randomNumber: Int
do {
randomNumber = randomInt(1, 5)
} while contains(temp, randomNumber)
temp.append(randomNumber)
}
This will be fine for tiny ranges like yours, but for larger ranges it will be very slow, because for the last few numbers you are waiting for the random number to hit precisely the remaining handful of possibilities. I just tried generating from a range of 200 in a playground and it took 9 seconds.
If you want a random selection of numbers with guaranteed coverage over a range, you could generate it like by taking that range and shuffling it, like this:
func shuffle<S: SequenceType>(source: S) -> [S.Generator.Element] {
var rangen = GeneratorOf { arc4random() }
let a = Array(Zip2(rangen, source))
return a.sorted { $0.0 < $1.0 }.map { $0.1 }
}
let min = 1, max = 5
shuffle(min...max)
If you want a selection of n non-repeating random numbers from a range 0..<m, there’s a particularly pretty algorithm to do this that generates an ascending sequence of random numbers from that range:
func randomGeneratorOf(#n: Int, #from: Int) -> GeneratorOf<Int> {
var select = UInt32(n)
var remaining = UInt32(from)
var i = 0
return GeneratorOf {
while i < from {
if arc4random_uniform(remaining) < select {
--select
--remaining
return i++
}
else {
--remaining
++i
}
}
return nil
}
}
Which you could use like so:
let engines = [
"Duck","Emily","Gordon","Henry", "Mavis",
"Belle","James","Edward","Thomas","Toby"
]
let picks = Array(randomGeneratorOf(n: 3, from: engines.count))
for engine in PermutationGenerator(elements: engines, indices: picks) {
println(engine)
}
Below is my suggestion.
I like this way since it is short and simple :)
let totalCount: Int = 150 //Any number you asssign
var randomNumArray: [Int] = []
var i = 0
while randomNumArray.count < totalCount {
i++
let rand = Int(arc4random_uniform(UInt32(totalCount)))
for(var ii = 0; ii < totalCount; ii++){
if randomNumArray.contains(rand){
print("do nothing")
} else {
randomNumArray.append(rand)
}
}
}