Swift 4 features code complete..

- implemented subscripts for LinkedLists and Tries.
- removed numerous references to IUO’s.
- refactored various unit tests to support subscripts and regular optionals.

Author: waynewbishop

Source/Factories/BSTree.swift

@@ -90,7 +90,7 @@ class BSTree<T: Comparable>{
     }
 
 
-    //equality test
+    //equality test - O(log n)
     func contains(_ key: T) -> Bool {
 
         var current: BSNode<T>? = root
@@ -194,6 +194,7 @@ class BSTree<T: Comparable>{
     //MARK: Balancing Methods
 
 
+    
     //determine if the tree is "balanced" - operations on a balanced tree is O(log n)
     func isTreeBalanced(for element: BSNode<T>?) -> Bool {
 

Source/Factories/LinkedList.swift

@@ -1,5 +1,5 @@
 //
-//  SwiftFactory.swift
+//  LinkedList.swift
 //  SwiftStructures
 //
 //  Created by Wayne Bishop on 6/7/14.
@@ -9,42 +9,32 @@
 import Foundation
 
 
-public class LinkedList<T: Equatable> {
+class LinkedList<T: Equatable> {
 
 
    //new instance
    private var head = LLNode<T>()
+   private var counter: Int  = 0
 
 
-  
-   var count: Int {
-        
-            if head.key == nil {
-                return 0
-            }
-                
-            else  {
-                
-                var current: LLNode = head
-                var x: Int = 1
-                
-                
-                //cycle through the list of items
-                while current.next != nil {
-                    current = current.next!
-                    x += 1
-                }
-                
-                return x
-                
-            }
+    
+    //the number of items - O(1)
+    var count: Int {
+        return counter
     }
+
 
+    //find subscript shortcut
+    subscript(index: Int) -> LLNode<T>? {
+        get {
+           return find(at: index)
+        }
+    }
 
 
     //empty list check
-    func isEmpty() -> Bool! {
-        return self.count == 0 || head.key == nil
+    func isEmpty() -> Bool {
+        return counter == 0 || head.key == nil
     }
 
 
@@ -56,6 +46,7 @@ public class LinkedList<T: Equatable> {
         //trivial check
         guard head.key != nil else {
             head.key = key
+            counter += 1
             return
         }
 
@@ -82,6 +73,7 @@ public class LinkedList<T: Equatable> {
 
         } //end while
 
+        counter += 1
     }
 
 
@@ -107,7 +99,7 @@ public class LinkedList<T: Equatable> {
 
 
     //obtain link at a specific index
-    func find(at index: Int) ->LLNode<T>! {
+    func find(at index: Int) ->LLNode<T>? {
 
 
         //check empty conditions
@@ -117,13 +109,13 @@ public class LinkedList<T: Equatable> {
 
 
         else  {
-            var current: LLNode<T>! = head
+            var current: LLNode<T> = head
             var x: Int = 0
 
 
             //cycle through elements
             while (index != x) {
-                current = current.next
+                current = current.next!
                 x += 1
             }
 
@@ -150,6 +142,7 @@ public class LinkedList<T: Equatable> {
         //establish the head node
         guard head.key != nil else {
             head.key = key
+            counter += 1
             return
         }
 
@@ -206,6 +199,8 @@ public class LinkedList<T: Equatable> {
 
         } //end while
 
+        counter += 1
+        
     }
 
 
@@ -253,6 +248,7 @@ public class LinkedList<T: Equatable> {
 
         } //end while
 
+        counter -= 1
 
     } //end function
 
@@ -325,8 +321,7 @@ public class LinkedList<T: Equatable> {
             if formula(current) == true {
                 results.append(element: current.key)
             }
-            
-            
+                        
             current = current.next
         }
 

Source/Factories/Queue.swift

@@ -8,11 +8,10 @@
 
 import Foundation
 
-public class Queue<T> {
-    
-   
-    private var top: Node<T>!
-    
+class Queue<T> {
+        
+    private var top: Node<T>?
+    private var counter: Int = 0
 
     init() {
       top = Node<T>()
@@ -21,24 +20,7 @@ public class Queue<T> {
 
     //the number of items
     var count: Int {
-        
-        guard top.key != nil else {
-            return 0
-        }
-        
-        
-        var current: Node<T> = top
-        var x: Int = 1
-
-        
-        //cycle through items
-        while current.next != nil {
-            current = current.next! //TODO: Add guard statement here..
-            x += 1
-        }
-        
-        return x
-        
+        return counter
     }
 
 
@@ -47,21 +29,19 @@ public class Queue<T> {
 
 
     //retrieve the top most item
-    func peek() -> T! {
-        return top.key
+    func peek() -> T? {
+        return top?.key
     }
 
 
 
     //check for the presence of a value
     func isEmpty() -> Bool {
 
-        guard top.key != nil else {
+        guard top?.key != nil else {
             return true
         }
-        
         return false
-        
     }
 
 
@@ -74,8 +54,9 @@ public class Queue<T> {
 
 
         //trivial case
-        guard top.key != nil else {
-            top.key = key
+        guard top?.key != nil else {
+            top?.key = key
+            counter += 1
             return
         }
 
@@ -92,7 +73,7 @@ public class Queue<T> {
         //append new item
         childToUse.key = key
         current?.next = childToUse
-        
+        counter += 1
     }
 
 
@@ -102,23 +83,24 @@ public class Queue<T> {
 
 
         //determine key instance
-        guard top.key != nil else {
+        guard top?.key != nil else {
             return nil
         }
 
-    
+        
         //retrieve and queue the next item
-        let queueItem: T? = top.key
+        let queueItem: T? = top?.key
 
 
         //use optional binding 
-        if let nextItem = top.next {
+        if let nextItem = top?.next {
           top = nextItem
         }
         else {
             top = Node<T>()
         }
 
+        counter -= 1
 
         return queueItem
 

Source/Factories/Stack.swift

@@ -59,7 +59,7 @@ class Stack<T> {
     func pop() {
 
         if self.count > 1 {
-            top = top.next!  //TODO: Add guard statement here..
+            top = top.next!
 
             //set counter
             counter -= 1

Source/Factories/Trie.swift

@@ -11,15 +11,19 @@ import Foundation
 
 public class Trie {
 
-    private var root: TrieNode!
+    private var root = TrieNode()
 
 
-    init(){
-        root = TrieNode()
+    //find subscript shortcut
+    subscript(word: String) -> Array<String>? {
+        get {
+            return find(word)
+        }
     }
 
 
 
+    
     //builds a tree hierarchy of dictionary content
     func append(word keyword: String) {
 
@@ -84,7 +88,7 @@ public class Trie {
 
 
     //find words based on the prefix
-    func find(_ keyword: String) -> Array<String>! {
+    func find(_ keyword: String) -> Array<String>? {
 
 
         //trivial case
@@ -129,15 +133,15 @@ public class Trie {
 
         //retrieve the keyword and any descendants
         if ((current.key == keyword) && (current.isFinal)) {
-            wordList.append(current.key)
+            wordList.append(current.key!)
         }
 
 
         //include only children that are words
         for child in current.children {
 
             if (child.isFinal == true) {
-                wordList.append(child.key)
+                wordList.append(child.key!)
             }
 
         }

Source/Structures/TrieNode.swift

@@ -10,8 +10,8 @@ import Foundation
 
 
 public class TrieNode {
-    
-    var key: String!
+        
+    var key: String?
     var children: Array<TrieNode>
     var isFinal: Bool
     var level: Int

SwiftStructures.xcodeproj/project.xcworkspace/xcuserdata/waynebishop.xcuserdatad/UserInterfaceState.xcuserstate

@@ -2,4 +2,22 @@
 <Bucket
    type = "1"
    version = "2.0">
+   <Breakpoints>
+      <BreakpointProxy
+         BreakpointExtensionID = "Xcode.Breakpoint.FileBreakpoint">
+         <BreakpointContent
+            shouldBeEnabled = "No"
+            ignoreCount = "0"
+            continueAfterRunningActions = "No"
+            filePath = "SwiftTests/TrieTest.swift"
+            timestampString = "527809210.612208"
+            startingColumnNumber = "9223372036854775807"
+            endingColumnNumber = "9223372036854775807"
+            startingLineNumber = "75"
+            endingLineNumber = "75"
+            landmarkName = "testFindNoExist()"
+            landmarkType = "7">
+         </BreakpointContent>
+      </BreakpointProxy>
+   </Breakpoints>
 </Bucket>