アルゴリズムを通じて よりよいアプリを

One of the "hidden" themes of WWDC 2018 was algorithms. This talk looks at some of the sessions that talked about using algorithms to make better code and shows a toy example of using algorithms using UICollectionView animation.

Transcript

1. ΞϧΰϦζϜΛ௨ͯ͡
   ΑΓΑ͍ΞϓϦΛ
   iOSDC 2018
   ϨΠɾϑΟοΫε
   @rayfix
   

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3. ΞϧΰϦζϜ͸
   ۀքͷֵ໋Λىͤ͜·͢!
   ϑΝΠϧ
   0 15 30 45 60
   ΦʔσΟΦσʔλ ѹॖ͞ΕͨΦʔσΟΦσʔλ
   

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4. ؾ͖ͮ·͔ͨ͠ʁ
   

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5. ALGORITHMS
   

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6. iOS 12 ϚʔέοτΠϯ
   • ΑΓ଎͘ɺΑΓ൓Ԡྑ͘
   
   • Ξχϝʔγϣϯ͕ҰஈͱεϜʔζʹ
   
   • ΞϓϦέʔγϣϯͷىಈ͕࠷େ40%଎͘
   
   • ΩʔϘʔυͷද͕ࣔ࠷େ50%଎͘
   
   • εϫΠϓʹΑΔΧϝϥͷىಈ͕࠷େ70%଎͘
   
   • ෛՙ࣌ͷڞ༗γʔτͷද͕ࣔ࠷େ2ഒ଎͘
   iPhone 5s
   

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7. O(1) ఆ਺࣌ؒ
   
   
   
   
   
   
   
   
   O(log n) ର਺
   O(n) ઢܗؔ਺
   O(n log n) ઢܗର਺
   O(n2) ೋ৐࣌ؒ
   O(nc) ଟ߲ࣜ࣌ؒ
   O(2n) ؒࢦ਺࣌ؒ
   O(n!) ֊৐ؔ਺
   ϥϯμ΢ͷه߸
   εέʔϧ͢Δ
   εέʔϧ͠ͳ͍
   

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8. O(1)
   
   
   
   
   
   
   
   
   O(log n)
   O(n)
   O(n log n)
   O(n2)
   O(nc)
   O(2n)
   O(n!)
   Auto Layout
   
   Session 202
   iOS 12
   

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9. Auto Layout
   ϨΞ΢τ੍໿ͷ਺
   ॲཧ࣌ؒ
   O(n)
   iOS 12
   

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10. Layout “Churn”
    class MyView: UIView {
    override func updateConstraints() {
    }
    }
    ϨΠΞ΢τ੍໿࠶ॳظԽʹ஫ҙ
    ̍ඵʹ̍̎̌ճݺͼग़͞ΕΔՄೳੑ͕͋Δ
    
    Session 220
    

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11. ίϨΫγϣϯΛޮՌతʹ
    ࢖༻͢Δํ๏
    • ஗Ԇॲཧ΍εϥΠεͷίετΛཧղ͠ͳ͕Βɺ

    ίϨΫγϣϯ࢖͍·͠ΐ͏
    
    • Swiftܕ ͱ FoundationܕͷؒʹϒϦοδ͕ඞཁͰ͢ɻ

    ίετ͸O(1) ͔ΒO(n) Ͱ͢ɻ
    let story = “σοΧ͍ string"
    let text = NSMutableAttributedString(string: story)
    let string = text.string
    Session 229
    

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12. ԕ͗ͨ͢ڮ
    let story = “σοΧ͍ string"
    let text = NSMutableAttributedString(string: story)
    let string = text.string
    as NSString
    for index in 1 ... {
    }
    let nsRange = string.range(of: “kitten")
    
    n
    InstrumentsͰܭΓ·͠ΐ͏
    

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13. ΞϧΰϦζϜΛड͚ೖΕΔ
    Crusty
    Dave Abrahams
    @DaveAbrahams
    
    Swift library designer / Professor of blowing-your-mind @apple
    @Mind your own business
    .
    Session 223
    

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14. γΣʔϓͷ࡟আ
    extension Canvas {
    mutating func deleteSelection() {
    for i in 0 ..< shapes.count {
    if shapes[i].isSelected {
    shapes.remove(at: i)
    }
    }
    }
    }
    

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15. γΣʔϓͷ࡟আ
    extension Canvas {
    mutating func deleteSelection() {
    for i in 0 ..< shapes.count {
    if shapes[i].isSelected {
    shapes.remove(at: i)
    }
    }
    }
    }
    TRAP
    

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16. γΣʔϓͷ࡟আ (V2)
    extension Canvas {
    mutating func deleteSelection() {
    var i = 0
    while i < shapes.count {
    if shapes[i].isSelected {
    shapes.remove(at: i)
    }
    i += 1
    }
    }
    }
    

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17. γΣʔϓͷ࡟আ (V2)
    extension Canvas {
    mutating func deleteSelection() {
    var i = 0
    while i < shapes.count {
    if shapes[i].isSelected {
    shapes.remove(at: i)
    }
    i += 1
    }
    }
    }
    ͋Εʁ
    

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18. γΣʔϓͷ࡟আ (V3)
    extension Canvas {
    mutating func deleteSelection() {
    var i = 0
    while i < shapes.count {
    if shapes[i].isSelected {
    shapes.remove(at: i)
    }
    else {
    i += 1
    }
    }
    }
    }
    
    

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19. γΣʔϓͷ࡟আ (V4)
    extension Canvas {
    mutating func deleteSelection() {
    for i in (0..if shapes[i].isSelected {
    shapes.remove(at: i)
    }
    }
    }
    }
    
    ͔͠͠…
    

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20. γΣʔϓͷ࡟আ (V4)
    extension Canvas {
    mutating func deleteSelection() {
    for i in (0..if shapes[i].isSelected {
    shapes.remove(at: i)
    }
    }
    }
    }
    O(n)
    O(n)
    O(n2) ೋ৐࣌ؒ
    

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21. Ϗοάɾσʔλ
    
    
    
    
    
    

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22. γΣʔϓͷ࡟আ (V5)
    extension Canvas {
    mutating func deleteSelection() {
    shapes.removeAll { $0.isSelected }
    }
    }
    O(n)
    

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23. ΩʔϙΠϯτ
    •ඪ४ϥΠϒϥϦͷΞϧΰϦζϜΛ

    ࢖ͬͨ΄͏͕෼͔Γ΍͍͢
    
    •ඪ४ϥΠϒϥϦͷΞϧΰϦζϜ͸ੑೳͷ

    ༧ଌੑ͕͋Δ
    
    •O(1) Ҏ֎͸ඞͣυΩϡϝϯτ͞Ε͍ͯΔ
    

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24. Raw LoopΛ࢖Θͳ͍
    http://sean-parent.stlab.cc/presentations/
    2013-09-11-cpp-seasoning/cpp-seasoning.pdf
    Sean Parent
    @SeanParent
    
    Software Engineer at Adobe
    C++ Seasoning
    

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25. Raw LoopΛ࢖Θͳ͍
    •ඪ४ͷΞϧΰϦζϜΛ࢖͏
    
    •ඪ४ͷΞϧΰϦζϜΛ࣮૷͢Δ
    
    •શͯͷίʔυ͸ϥΠϒϥϦʔԽ͢Δ
    
    •৽͍͠ΞϧΰϦζϜΛ։ൃ͢Δ
    
    •༗໊ʹͳΔ

    

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26. ׽ࣈ͕೉͍͠
    cards.shuffle()
    let shuffledIndices = cards.indices.shuffled()
    ฤूεςοϓ
    for (new, orig) in shuffledIndices.enumerated() {
    newCards[new] = originalCards[orig]
    }
    collectionView.performBatchUpdates({
    for ( ) in shuffledIndices.enumerated() {
    let src = IndexPath(item: orig, section: 0)
    let dst = IndexPath(item: new, section: 0)
    collectionView.moveItem(at: src, to: dst)
    }
    }, completion: nil)
    new
    orig,
    Session 225
    όά
    ʢnew, orig)
    ͕ਖ਼͍͠
    

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27. ࠓ೔ͷӳޠڭࣨ
    

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28. ΤϏϯάϋ΢ε๨٫ۂઢ
    R = e− t
    S
    

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29. zip
    2
    ( )
    ,
    0
    ( )
    ,
    1
    ( )
    ,
    4
    ( )
    ,
    3
    ( )
    ,
    

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30. sort
    2
    ( )
    ,
    0
    ( )
    ,
    1
    ( )
    ,
    4
    ( )
    ,
    3
    ( )
    ,
    

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31. δΣωϦοΫʹ
    extension Collection {
    func sortedWithIndices(by order: (Element, Element) -> Bool) ->
    ([Element], moves: [(from: Index, to: Index)]) {
    let elementsAndIndices = zip(self, self.indices)
    let sorting = elementsAndIndices.sorted { order($0.0, $1.0) }
    let elements = sorting.map { $0.0 }
    let moves = sorting.enumerated().map {
    (offset, element) -> (from: Index, to: Index) in
    var toIndex: Index = startIndex
    formIndex(&toIndex, offsetBy: offset)
    let fromIndex: Index = element.1
    return (from: fromIndex, to: toIndex)
    }.filter { $0.from != $0.to }
    return (elements, moves: moves)
    }
    }
    

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32. ࠩ෼ϥΠϒϥϦʔ
    • DeepDiff
    
    • Differ
    
    • DifferenceKit
    
    • IGListKit
    
    • RxDataSources
    DifferenceKit
    Heckel’s Algorithm O(n)
    

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34. Summary
    •ΞϧΰϦζϜΛษڧ͠·͠ΐ͏
    
    •ඪ४ϥΠϒϥϦʔΛಡΈ·͠ΐ͏
    
    •Raw Loop Λආ͚·͠ΐ͏
    

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35. ͝੩ௌ
    ͋Γ͕ͱ͏͍͟͝·ͨ͠!
    

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