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mitghimitghi
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Merge pull request kodecocodes#3 from hollance/master
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2 parents 67a3dc9 + cfb94d0 commit 004e513

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24 files changed

+850
-18
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‎Deque/Deque.playground/Contents.swift

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//: Playground - noun: a place where people can play
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public struct Deque<T> {
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private var array = [T]()
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public var isEmpty: Bool {
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return array.isEmpty
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}
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public var count: Int {
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return array.count
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}
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public mutating func enqueue(element: T) {
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array.append(element)
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}
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public mutating func enqueueFront(element: T) {
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array.insert(element, atIndex: 0)
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}
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public mutating func dequeue() -> T? {
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if isEmpty {
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return nil
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} else {
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return array.removeFirst()
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}
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}
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public mutating func dequeueBack() -> T? {
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if isEmpty {
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return nil
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} else {
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return array.removeLast()
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}
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}
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public func peekFront() -> T? {
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return array.first
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}
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public func peekBack() -> T? {
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return array.last
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}
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}
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var deque = Deque<Int>()
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deque.enqueue(1)
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deque.enqueue(2)
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deque.enqueue(3)
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deque.enqueue(4)
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deque.dequeue() // 1
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deque.dequeueBack() // 4
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deque.enqueueFront(5)
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deque.dequeue() // 5

‎Deque/Deque.playground/contents.xcplayground

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<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
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<playground version='5.0' target-platform='osx'>
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<timeline fileName='timeline.xctimeline'/>
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</playground>

‎Deque/Deque.playground/timeline.xctimeline

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<?xml version="1.0" encoding="UTF-8"?>
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<Timeline
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version = "3.0">
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<TimelineItems>
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</TimelineItems>
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</Timeline>

‎Deque/Deque.swift

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/*
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Deque (pronounced "deck"), a double-ended queue
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This particular implementation is simple but not very efficient. Several
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operations are O(n). A more efficient implementation would use a doubly
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linked list or a circular buffer.
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*/
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public struct Deque<T> {
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private var array = [T]()
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public var isEmpty: Bool {
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return array.isEmpty
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}
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public var count: Int {
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return array.count
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}
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public mutating func enqueue(element: T) {
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array.append(element)
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}
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public mutating func enqueueFront(element: T) {
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array.insert(element, atIndex: 0)
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}
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public mutating func dequeue() -> T? {
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if isEmpty {
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return nil
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} else {
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return array.removeFirst()
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}
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}
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public mutating func dequeueBack() -> T? {
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if isEmpty {
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return nil
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} else {
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return array.removeLast()
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}
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}
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public func peekFront() -> T? {
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return array.first
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}
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public func peekBack() -> T? {
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return array.last
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}
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}

‎Deque/README.markdown

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# Deque
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A double-ended queue. For some reason this is pronounced as "deck".
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A regular [queue](../Queue/) adds new elements to the back and dequeues from the front. The deque also allows enqueuing at the front and dequeuing from the back, and peeking at both ends.
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Here is a very basic implementation of a deque in Swift:
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```swift
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public struct Deque<T> {
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private var array = [T]()
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public var isEmpty: Bool {
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return array.isEmpty
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}
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public var count: Int {
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return array.count
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}
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public mutating func enqueue(element: T) {
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array.append(element)
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}
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public mutating func enqueueFront(element: T) {
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array.insert(element, atIndex: 0)
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}
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public mutating func dequeue() -> T? {
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if isEmpty {
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return nil
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} else {
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return array.removeFirst()
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}
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}
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public mutating func dequeueBack() -> T? {
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if isEmpty {
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return nil
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} else {
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return array.removeLast()
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}
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}
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public func peekFront() -> T? {
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return array.first
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}
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public func peekBack() -> T? {
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return array.last
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}
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}
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```
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This uses an array internally. Enqueuing and dequeuing is simply a matter of adding and removing items from the front or back of the array.
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An example of how to use it in a playground:
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```swift
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var deque = Deque<Int>()
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deque.enqueue(1)
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deque.enqueue(2)
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deque.enqueue(3)
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deque.enqueue(4)
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deque.dequeue() // 1
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deque.dequeueBack() // 4
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deque.enqueueFront(5)
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deque.dequeue() // 5
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```
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This particular implementation of `Deque` is simple but not very efficient. Several operations are **O(n)**, notably `enqueueFront()` and `dequeue()`. I've included it only to show the principle of what a deque does.
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A more efficient implementation would use a [doubly linked list](../Linked List/), a [circular buffer](../Ring Buffer/), or two [stacks](../Stack/) facing opposite directions.
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*Written for Swift Algorithm Club by Matthijs Hollemans*

‎Ordered Array/OrderedArray.playground/Contents.swift

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//: Playground - noun: a place where people can play
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public struct OrderedArray<T: Comparable> {
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private var array = [T]()
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public init(array: [T]) {
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self.array = array.sort()
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}
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public var isEmpty: Bool {
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return array.isEmpty
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}
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public var count: Int {
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return array.count
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}
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public subscript(index: Int) -> T {
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return array[index]
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}
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public mutating func removeAtIndex(index: Int) -> T {
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return array.removeAtIndex(index)
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}
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public mutating func removeAll() {
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array.removeAll()
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}
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public mutating func insert(newElement: T) -> Int {
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let i = findInsertionPoint(newElement)
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array.insert(newElement, atIndex: i)
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return i
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}
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/*
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// Slow version that looks at every element in the array.
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private func findInsertionPoint(newElement: T) -> Int {
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for i in 0..<array.count {
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if newElement <= array[i] {
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return i
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}
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}
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return array.count
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}
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*/
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// Fast version that uses a binary search.
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private func findInsertionPoint(newElement: T) -> Int {
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var range = 0..<array.count
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while range.startIndex < range.endIndex {
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let midIndex = range.startIndex + (range.endIndex - range.startIndex) / 2
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if array[midIndex] == newElement {
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return midIndex
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} else if array[midIndex] < newElement {
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range.startIndex = midIndex + 1
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} else {
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range.endIndex = midIndex
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}
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}
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return range.startIndex
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}
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}
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extension OrderedArray: CustomStringConvertible {
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public var description: String {
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return array.description
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}
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}
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var a = OrderedArray<Int>(array: [5, 1, 3, 9, 7, -1])
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a // [-1, 1, 3, 5, 7, 9]
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a.insert(4) // inserted at index 3
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a // [-1, 1, 3, 4, 5, 7, 9]
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a.insert(-2) // inserted at index 0
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a.insert(10) // inserted at index 8
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a // [-2, -1, 1, 3, 4, 5, 7, 9, 10]
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‎Ordered Array/OrderedArray.playground/contents.xcplayground

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<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
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<playground version='5.0' target-platform='osx'>
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<timeline fileName='timeline.xctimeline'/>
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</playground>

‎Ordered Array/OrderedArray.playground/timeline.xctimeline

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<?xml version="1.0" encoding="UTF-8"?>
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<Timeline
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version = "3.0">
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<TimelineItems>
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</TimelineItems>
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</Timeline>

‎Ordered Array/OrderedArray.swift

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/*
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An ordered array. When you add a new item to this array, it is inserted in
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sorted position.
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*/
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public struct OrderedArray<T: Comparable> {
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private var array = [T]()
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public init(array: [T]) {
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self.array = array.sort()
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}
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public var isEmpty: Bool {
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return array.isEmpty
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}
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public var count: Int {
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return array.count
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}
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public subscript(index: Int) -> T {
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return array[index]
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}
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public mutating func removeAtIndex(index: Int) -> T {
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return array.removeAtIndex(index)
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}
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public mutating func removeAll() {
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array.removeAll()
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}
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public mutating func insert(newElement: T) -> Int {
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let i = findInsertionPoint(newElement)
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array.insert(newElement, atIndex: i)
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return i
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}
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private func findInsertionPoint(newElement: T) -> Int {
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var range = 0..<array.count
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while range.startIndex < range.endIndex {
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let midIndex = range.startIndex + (range.endIndex - range.startIndex) / 2
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if array[midIndex] == newElement {
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return midIndex
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} else if array[midIndex] < newElement {
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range.startIndex = midIndex + 1
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} else {
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range.endIndex = midIndex
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}
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}
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return range.startIndex
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}
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}
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extension OrderedArray: CustomStringConvertible {
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public var description: String {
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return array.description
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}
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}

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