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Showing posts from September, 2021

Printing Staircase Pattern : Swift coding challenge

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In this post, we can try interesting pattern printing challenge in Swift. The problem statement goes like this " Print a staircase of given size 'n'. Make sure that its base and height are both equal to n, and the image is drawn only using `#` symbols and spaces. The last line is not preceded by any spaces." Expected Output : # ## ### #### ##### ###### Working solution: func makePatternOf ( _ size : Int ) { var str = "" // 1 for index in ( 0 ..< size ) { let stop = size -index-1; // 2 for _ in 0 ..< stop { str. append ( " " ) ; } // 3 for _ in 0 .. . index { str. append ( "#" ) ; } print ( str ) str = "" } } makePatternOf ( 6 ) Loop to visit every row of stair case. Loop for appe...
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HackerRank Challenges : Migratory Birds solution in Swift

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In this post solution written in Swift for Migratory Bird Practice challenge from HackerRank. The problem statement goes like this - "Given an array of bird sightings where every element represents a bird type id, determine the id of the most frequently sighted type. If more than 1 type has been spotted that maximum amount, return the smallest of their ids"  For Example, Given array [1, 1, 2, 3, 3] There are two each of types 1 and 3, and one sighting of type 2. Pick the lower of the two types seen twice: type 1. Working solution in Swift 5.0:      func   migratoryBirds ( arr :   [ Int ])   ->   Int   {          // Write your code here          var   dict : [ String :   Int ]   =   [ : ]          // 1          arr . forEach ({  ...
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Codility Challenge : Tennis tournament

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In this post, we have Swift 5.0 solution for - Given the number of players P and the number of reserved courts C, returns the maximum number of games that can be played in parallel. For Example, Given P = 5 players and C = 3 available courts, the function should return 2. Working solution :      public func solution ( _ P: Int , _ C: Int ) -> Int {     // 1     if P < 2 || C < 1 {       return 0     }          // 2     return P >= (C * 2 ) ? C : (P / 2 ) % C   }    solution ( 5 , 3 ) // returns 2 When insufficient Players or Courts, games can not be played. If total players exceeds courts capacity, all courts occupied & games will be played. Otherwise return total number of games played from Players strength. Full detail of exercise challenge : https://app.codility.com/programmers/trainings/3/tennis_tournament/ Happy coding !
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Codility National Coding Week Sep-2021 : String transformation solution in Swift

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In this post Swift 5.0 solution given for National Coding Week Sep-2021 challenge. Given a string S of letters 'a' and/or 'b', replaces some consecutive sequence "abb" in S by "baa". Example,  S = "ababb" then  "ababb" → "abbaa" → "baaaa". Working solution :      public func solution ( _ S : inout String ) -> String {       var hasFound = true       var res = Array(S)       // 1       while hasFound && res.count > 2 {         hasFound = false         //2         for index in 0 ..<res.count- 2 {           // 3           if res[index] == "a" && res[index+ 1 ] == "b" && res[index+ 2 ] == "b" {             hasFound = true             res[index] = "b"         ...
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Codility Challenge : Find longest sequence of zeros in binary representation of an integer (Binary gap)

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In this post Swift 5.0 solution given for the Codility exercise. Solving Binary gap for given positive integer. For example, number 9 has binary representation 1001 and contains a binary gap of length 2. Complete details of exercise  :  https://app.codility.com/programmers/lessons/1-iterations/binary_gap/ Here is the working solution:      public func solution ( _ N : Int ) -> Int {              var max_gap: UInt = 0       var current_gap: UInt = 0               // 1       let binSequence = Array(String(N, radix: 2 ))       var index = 0              while index < binSequence.count {                  // 2         if binSequence[index] == "1" {                      // 3...
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Animating label text update - choosing a better way

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Recently I published a countdown app .  At one point of development - I have to show a timer on a UILabel which ticks on each seconds. As usual I started  setting text to a label object - self .timerLabel.text = someString Easy piece of cake right !?   But wait ... it won't take much user attention when timer ticks on every seconds. So I decided to make use of a simple animation while label gets text update. I found there are dozens of ways to animate a label. In this short article, I listed 3 best way you can animate text on a label. ( Spoiler Alert 👀- I decided to go with 3rd option)  1. Fade In - Fade out animation : CATransition class has got transition type `fade`. With timing function of CATransition - I was able to see the below result. let animation: CATransition = CATransition () animation.timingFunction = CAMediaTimingFunction (name: CAMediaTimingFunctionName .easeInEaseOut) animation.type = CATransitionType .fade animation.subtype = C...
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Prevent Navigationbar or Tabbar overlapping Subview - solved for Card view

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Recently, I started with a Card view added as a subview of UIView in a view-controller. When a view controller created along subviews, it tends to use entire screen bounds and also slips behind Tab bar or Navigation bar. In my current situation, it's second case. Casually new iOS developers will write a patch by additional value for coordinate y and subtracting bar height from its size. A lot of them posted in SO threads too : How to prevent UINavigationBar from covering top of view? View got hidden below UINavigationBar iOS 7 Navigation Bar covers some part of view at Top So, how I got solved ? self.edgesForExtendedLayout = [] This  will avoid all subviews in a view controller get behind any bars. Read full apple  documentation on here. Full Source code below :  //Simple view controller where its view layed-out as a card. class WidgetCardViewController : UIViewController { var containerView = UIView () //MARK:- View Controller Life Cyc...
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UICollectionViewCell shows with wrong size on First time - Solved

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We commonly use Collection view where its cell size calculated run time. The flow layout delegate is responsible to return individual cell sizes. BUT in most of the cases, delegate method `collectionView: layout sizeForItem:` expects cell size too early. Before generating actual cell size. extension YourViewController : UICollectionViewDelegateFlowLayout { func collectionView ( _ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize { return CGSize (width: externalWidth, height: externalHeight) } } For instance, if a cell size depends on external view and its frame is not yet ready - results with wrong (or outdated) cell size. Typically happens for the first time view controller laid out all views. You can find similar queries in StackOverflow community : Collection view sizeForItemNotWorking UICollectionViewCell content wrong size on first load How to refresh UICollec...
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Implementing autocompletion OTP field in iOS

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Long waiting is over. !!  iOS 12 brings Autofill for OTP text field which is close to Android provided a decade back. Previously in iOS we used to toggle between OTP text screen and message inbox.  Which was hard to remember and time consuming resulting a bad user experience. Personally, I have been asked from the client/customer couple of times to implement autocompletion for OTP field and took me a lot of time to convey that it is not possible in iOS. Why Autofill was not possible previously?  We all know that Apple gives at most care for user privacy. When we see iOS architecture, each individual app is like a separate island. There is no inter-app bridge between apps (exception for Keychain and URLSchemes APIs which gives very limited scope). Thus we cannot read message content from inbox. Where to start Autofilling? First of all, the target SMS need to have the OTP Code with prefix string "Code" or "Passcode"on its message content. Beware of OTP c...
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Static variable vs Class variable in Swift

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How Static properties differs to usual properties ? Used to create type properties with either let or var. These are shared between all objects of a class.  During class loading time, a single memory location allocated for the property if we declared as static. Static property belongs to a class (or struct) Type rather than Instance of class (or struct). Hence it also called  Type Properties What if we declare "static var" ? Since it's a variable, we can change it in future even after initialised. When we change the value of the static variable property, that property is now changed in all future instances. What if we declare "static let" ? static let instance : Singleton = Singleton() Since it's constant, we cannot change once initialised. Its value will remain same even if we share among all the instance or object of a class or struct. Useful to adopt singleton pattern. How class variables differ static variables ? It dif...
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