Data Types and Collection Data Structures in Swift

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Data Types and Collection Data Structures in Swift Spandana Batchu

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Agenda • Class Vs Struct - Dimensions of Performance  • Big O Notation • Collection Data Structures 

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Big O Notation O(1) Constant time O(log n) Logarithmic O(n) Linear O(n (log n)) Linearithmic O( n ) Constant time 2 O(2^n) Exponential O(n!) Factorial

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DEMO Download Demo Project at : https://github.com/spandanabatchu/BigONotation 

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Collection Data Structures Arrays Dictionary Set

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Array Use Array when the order of variables matters Creating an Array with a default value: var threeDoubles = Array(repeating: 0.0, count: 3) // threeDoubles is of type [Double], and equals [0.0, 0.0, 0.0] It is good practice to create immutable collections in all cases Where the collection does not need to change

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Dictionary When there isn’t a particular order to what you need to store, but the data has meaningful association.

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Set When uniqueness matters, but order does not.

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var favoriteGenres: Set = ["Rock", "Classical", "Hip hop”] // favoriteGenres has been initialised with three initial values Set A set type cannot be inferred from an array literal alone, so the type Set must be explicitly declared. var favoriteGenres: Set = ["Rock", "Classical", "Hip hop"]

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Fundamental set operations

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let oddDigits: Set = [1, 3, 5, 7, 9] let evenDigits: Set = [0, 2, 4, 6, 8] let singleDigitPrimeNumbers: Set = [2, 3, 5, 7] oddDigits.union(evenDigits).sorted() // [0, 1, 2, 3, 4, 5, 6, 7, 8, 9] oddDigits.intersection(evenDigits).sorted() // [] oddDigits.subtracting(singleDigitPrimeNumbers).sorted() // [1, 9] oddDigits.symmetricDifference(singleDigitPrimeNumbers).sorted() // [1, 2, 9]

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POP QUIZ

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What would you use to create a list of every author in the library?

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A Set! It automatically removes duplicate names, which means you can enter every single author's name as many times as you want, but you'll still have only a single entry. Once you create the Set, you can use set.allObjects to access the Array of unique names.

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How would you store the most popular book by each author?

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A Dictionary! If you use the author's name as the key and the title of that author's most popular book as the value, you can access the most popular book by any author like this: mostPopularBooks["Gillian Flynn"] //Returns "Gone Girl"

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How would you store the alphabetically sorted titles of a proliﬁc author's entire body of work?

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An Array! Since you're in a situation where you have a number of similar objects (all titles are Strings) and their order matters (titles must be sorted alphabetically) this is an ideal case for an Array.

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THANK YOU! References:  Understanding Swift Performance - WWDC 2016  Collection Data Structures in Swift - Raywenderlich Download Demo Project at : https://github.com/spandanabatchu/BigONotation 