Swift and Big O homework

20160124 Homework.playground/Contents.swift

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+//: Playground - noun: a place where people can play
+
+import UIKit
+
+var str = "Hello, playground"
+
+/* 
+
+/*

20160124 Homework.playground/contents.xcplayground

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

20160124 Homework.playground/timeline.xctimeline

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

20160124-homework-recursion.playground/Contents.swift

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+// Exercises from: https://docs.google.com/document/d/1INvOynuggw69yLRNg3y-TPwBiYb3lQZQiFUOxZKBwsY/edit#
+
+import UIKit
+import Foundation
+
+/* 1) Write an iterative (not recursive) fibonacci function that calculates the nth fibonacci number. How does its performance compare with the non-memoized recursive one (see Appendix A below), based on the number of iterations that Swift says it takes in the right margin?
+
+Note: In the Fibonacci sequence, each number is the sum of the two previous numbers. 
+ie: [0, 1, 1, 2, 3, 5, 8, 13, 21, 34] */
+
+//Appendix A: Recursive Fibonacci from class (non-memoized)
+func fib1(n: Int) -> Int {
+    if (n == 0 || n == 1) {
+        return 1
+    }
+    return fib1(n - 1) + fib1(n - 2)
+}
+print(fib1(10))
+(0...5).map { i in fib1(i) } // create map
+
+// Answer: this non recursive method is waaay faster.
+
+var fibNo = 1
+var index = 0
+
+func fib2(numbers: Int) -> Int {
+
+for number in 1...numbers { // loop through numbers 1...10
+    print("index \(number): \(fibNo)")
+    let temp = fibNo + index
+    index = fibNo
+    fibNo = temp
+    }
+return fibNo
+}
+
+
+
+print(fib2(10)) // Note: this is actually returning the 11th fib no because the function is starting with a 0 indexed number
+
+/* 2) The engineers have been hard at work on the clumsy robot project, and have released a new API with a new tryStep method (see Appendix B). Now it returns an Int, which is -1 if the robot fell down a step, 0 if the robot stayed on the same step, or 1 if the robot went to the next step. Write a new stepUp method using this new tryStep method that works the same as before. */
+
+// Original Program: 
+/*
+var stepNum = 0
+func tryStep() -> Bool {
+    let success = Int(arc4random_uniform(2)) > 0 // generate rando number
+    if (success) {
+        stepNum++
+        print("Yay! \(stepNum)")
+    } else {
+        stepNum--;
+        print("Ow!  \(stepNum)")
+    }
+    return success
+}
+
+func stepUp() {
+    if tryStep() {
+        // We’re done!
+        return
+    }
+    // Now we’re two steps below where we want to be :-(
+    stepUp()
+    stepUp()
+}
+print(stepUp())
+*/
+
+// Appendix B:
+var steppNum = 0
+
+func tryStepp() -> Int {
+    let stepCount = Int(arc4random_uniform(3)) - 1 // generate rando number
+    steppNum += stepCount;
+
+    switch(stepCount) {
+    case -1: print("Ouch \(steppNum)")
+    case 1: print("Yay  \(steppNum)")
+    default: print("Beep \(steppNum)")
+    }
+    return stepCount
+}
+
+//// My code:
+//func steppUp(var stepsTaken: Int = 0) {
+//    stepsTaken += tryStepp()
+//    if stepsTaken == 1 {
+//        // we're done!
+//        return
+//    }
+//    steppUp(stepsTaken)
+//}
+//steppUp()
+
+// Cameron's Code:
+func stepUp() {
+    switch tryStepp() {
+    case 1:
+        return
+    case -1:
+        stepUp()
+        stepUp()
+    default:
+        stepUp()
+    }
+}
+stepUp()
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20160124-homework-recursion.playground/contents.xcplayground

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

20160124-homework-recursion.playground/timeline.xctimeline

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

20160128-homework-merge-sort.playground/Contents.swift

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+//: Playground - noun: a place where people can play
+
+import Foundation
+
+var str = "Hello, playground"
+
+/* 
+
+Use recursion to implement Insertion Sort in Swift:
+
+Requirements:
+You may not use loops
+Your implementations should be in-place (try not to create additional arrays)
+You should implement and use additional helper functions
+
+Tips:
+Add additional parameters to your helper functions to pass information between recursive calls
+You can use the swap function to exchange two values in a mutable (var) array:
+
+var array = [1, 2]
+swap(&array[0], &array[1])
+array // [2, 1]
+
+// Insertion Sort from Stack Overflow: 
+public static int[] RecursiveInsertionSort(int[] array, int n) {
+int i;
+if (n > 1)
+RecursiveInsertionSort(array, n - 1);
+else {
+int k = array[n];
+i = n - 1;
+while (i >= 0  & &  array[i] > k) {
+array[i + 1] = array[i];
+i = i - 1;
+}
+array[i + 1] = k;
+}
+return array;
+}
+*/
+
+// regular insertion sort:
+func exchange<T>(inout data: [T], i:Int, j:Int) {
+    let temp:T = data[i]
+    data[i] = data[j]
+    data[j] = temp
+}
+
+func insertionSort(var unsortedArray:Array<Int>)->Array<Int>{
+    if(unsortedArray.count<2) {
+        return unsortedArray
+    }
+    for var j = 1; j < unsortedArray.count; j++ {
+        var i = j
+        while i>0 && unsortedArray[i-1]>unsortedArray[i] {
+            exchange(&unsortedArray, i: i-1, j: i)
+            i--;
+        }
+    }
+    return unsortedArray;
+}
+insertionSort([3, 4, 5, 1, 2])
+
+// Cameron's notes for homework:
+func printAllElements(values: [Int]) {
+    for value in values {
+        print(value)
+    }
+}
+
+func printAllElementsRecursive(values: [Int]) {
+    printElementsHelper(values, index: 0)
+}
+
+func printElementsHelper(values: [Int], index: Int) {
+    if index < values.count {
+        print(values[index])
+        printElementsHelper(values, index: index + 1)
+    }
+}
+
+func setValue(inout array: [Int], value: Int, atIndex index: Int) {
+    array[index] = value
+}
+
+var values = [10, 20, 30]
+printAllElements(values)
+
+setValue(&values, value: 100, atIndex: 1)
+values
+
+
+
+func reverse(inout array: [Int]) {
+    for i in 0..<array.count / 2 {
+        swap(&array[i], &array[array.count - i - 1])
+    }
+}
+
+reverse(&values)
+values
+
+
+// 2) 
+
+let blacklist: Set<String> = ["crapple", "fandroid", "m$"]
+
+func moderate(message: String) -> Bool {
+
+    let words = (message as NSString).componentsSeparatedByString(" ")
+    for word in words {
+        if blacklist.contains(word.lowercaseString) {
+            return false
+        }
+    }
+    return true
+}
+moderate("I would never use a crApple product!")
+moderate("something else")
+
+// 3) 
+
+protocol PhoneBookProtocol {
+    mutating func addPerson(name: String, phoneNumber: String)
+    mutating func removePerson(name: String)
+    mutating func importFrom(oldPhonebook: [(String, String)])
+    func findPerson(name: String) -> String? // Return phone #
+}
+
+class PhoneBook: PhoneBookProtocol {
+    var storage: [String : String] = [:] // @{}
+    //var storage = Dictionary<String, String>()
+    func addPerson(name: String, phoneNumber: String) {
+        storage[name] = phoneNumber
+    }
+
+    func removePerson(name: String) {
+        storage.removeValueForKey(name)
+    }
+
+    func findPerson(name: String) -> String? {
+        return storage[name]
+    }
+
+    func importFrom(oldPhonebook: [(String, String)]) {
+        for entry in oldPhonebook {
+            addPerson(entry.0, phoneNumber: entry.1)
+        }
+    }
+}
+
+
+let oldData = [("Caleb", "501-555-1234"), ("Mike", "212-555-4321"), ("Jenny", "345-867-5309")]
+
+let phoneBook = PhoneBook()
+phoneBook.importFrom(oldData)
+
+phoneBook.findPerson("Jenny")
+

20160128-homework-merge-sort.playground/contents.xcplayground

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

20160128-homework-merge-sort.playground/timeline.xctimeline

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