Merge pull request kodecocodes#82 from Satre95/TernarySearchTree

Ternary search tree

Author: Chris Pilcher

Ternary Search Tree/README.markdown

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+# Ternary Search Tree
+
+Data structure and simple test in playground has been implemented. 
+Documentation and examples coming soon!! :)

Ternary Search Tree/TST.playground/Contents.swift

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+//: Playground - noun: a place where people can play
+
+import Cocoa
+import Foundation
+
+let treeOfStrings = TernarySearchTree<String>()
+let allowedChars = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"
+
+//Random string generator from:
+//http://stackoverflow.com/questions/26845307/generate-random-alphanumeric-string-in-swift/26845710
+func randomAlphaNumericString(length: Int) -> String {
+    let allowedCharsCount = UInt32(allowedChars.characters.count)
+    var randomString = ""
+    
+    for _ in (0..<length) {
+        let randomNum = Int(arc4random_uniform(allowedCharsCount))
+        let newCharacter = allowedChars[allowedChars.startIndex.advancedBy(randomNum)]
+        randomString += String(newCharacter)
+    }
+    
+    return randomString
+}
+
+var testStrings: [(key:String, data:String)] = []
+let testCount = 30
+for _ in (1...testCount) {
+    let randomLength = Int(arc4random_uniform(10))
+    let key = randomAlphaNumericString(randomLength)
+    let data = randomAlphaNumericString(randomLength)
+//    print("Key: \(key) Data: \(data)")
+    
+    if key != "" && data != "" {
+        testStrings.append((key, data))
+        treeOfStrings.insert(data, withKey: key)
+    }
+}
+
+for aTest in testStrings {
+    let data = treeOfStrings.find(aTest.key)
+    
+    if data == nil {
+        print("TEST FAILED. Key: \(aTest.key) Data: \(aTest.data)")
+    }
+    if data != aTest.data {
+        print("TEST FAILED. Key: \(aTest.key) Data: \(aTest.data)")
+    }
+}
+
+var testNums: [(key: String, data: Int)] = []
+let treeOfInts = TernarySearchTree<Int>()
+for _ in (1...testCount) {
+    let randomNum = Int(arc4random_uniform(UInt32.max))
+    let randomLength = Int(arc4random_uniform(10))
+    let key = randomAlphaNumericString(randomLength)
+    
+    if key != "" {
+        testNums.append((key, randomNum))
+        treeOfInts.insert(randomNum, withKey: key)
+    }
+}
+
+for aTest in testNums {
+    let data = treeOfInts.find(aTest.key)
+    if data == nil {
+        print("TEST FAILED. Key: \(aTest.key) Data: \(aTest.data)")
+    }
+    if data != aTest.data {
+        print("TEST FAILED. Key: \(aTest.key) Data: \(aTest.data)")
+    }
+}
+

Ternary Search Tree/TST.playground/Sources/TSTNode.swift

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+//
+//  TSTNode.swift
+//  
+//
+//  Created by Siddharth Atre on 3/15/16.
+//
+//
+
+import Foundation
+
+class TSTNode<Element> {
+    //Member properties of a particular node.
+    var key: Character
+    var data: Element?
+    var hasData: Bool
+    
+    //Children
+    var left: TSTNode?, right: TSTNode?, middle: TSTNode?
+    
+    
+    init(key: Character, data: Element?) {
+        self.key = key
+        self.data = data
+        self.hasData = (data != nil)
+    }
+    
+    init(key:Character) {
+        self.key = key
+        self.data = nil
+        self.hasData = false
+    }
+    
+}

Ternary Search Tree/TST.playground/Sources/TernarySearchTree.swift

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+//
+//  TernarySearchTree.swift
+//  
+//
+//  Created by Siddharth Atre on 3/15/16.
+//
+//
+
+import Foundation
+
+
+public class TernarySearchTree<Element> {
+    
+    var root: TSTNode<Element>?
+    
+    public init() {}
+    
+    //MARK: - Insertion
+    
+    public func insert(data:Element, withKey key: String) -> Bool{
+        return insertNode(&root, withData: data, andKey: key, atIndex: 0)
+        
+    }
+    
+    private func insertNode(inout aNode: TSTNode<Element>?, withData data: Element, andKey key: String, atIndex charIndex: Int) -> Bool {
+        
+        //sanity check.
+        if(key.characters.count == 0) {
+            return false
+        }
+        
+        //create a new node if necessary.
+        if(aNode == nil) {
+            let index = key.startIndex.advancedBy(charIndex)
+            aNode = TSTNode<Element>(key: key[index])
+        }
+        
+        //if current char is less than the current node's char, go left
+        let index = key.startIndex.advancedBy(charIndex)
+        if(key[index] < aNode!.key) {
+            return insertNode(&aNode!.left, withData: data, andKey: key, atIndex: charIndex)
+        }
+            //if it's greater, go right.
+        else if(key[index] > aNode!.key) {
+            return insertNode(&aNode!.right, withData: data, andKey: key, atIndex: charIndex)
+        }
+            //current char is equal to the current nodes, go middle
+        else {
+            //continue down the middle.
+            if(charIndex + 1 < key.characters.count) {
+                return insertNode(&aNode!.middle, withData: data, andKey: key, atIndex: charIndex + 1)
+            }
+                //otherwise, all done.
+            else {
+                aNode!.data = data
+                aNode?.hasData = true
+                return true
+            }
+        }
+    }
+    
+    
+    //MARK: - Finding
+    
+    
+    public func find(key:String) -> Element? {
+        return findNode(root, withKey: key, atIndex: 0)
+    }
+    
+    
+    private func findNode(aNode: TSTNode<Element>?, withKey key: String, atIndex charIndex: Int) -> Element? {
+        
+        //Given key does not exist in tree.
+        if aNode == nil {
+            return nil
+        }
+        
+        let index = key.startIndex.advancedBy(charIndex)
+        //go left
+        if key[index] < aNode!.key {
+            return findNode(aNode!.left, withKey: key, atIndex: charIndex)
+        }
+            //go right
+        else if key[index] > aNode!.key {
+            return findNode(aNode!.right, withKey: key, atIndex: charIndex)
+        }
+            //go middle
+        else {
+            if charIndex + 1 < key.characters.count {
+                return findNode(aNode!.middle, withKey: key, atIndex: charIndex + 1)
+            } else {
+                return aNode!.data
+            }
+        }
+    }
+}

Ternary Search Tree/TST.playground/contents.xcplayground

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

Ternary Search Tree/TST.playground/timeline.xctimeline

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

Ternary Search Tree/TSTNode.swift

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+//
+//  TSTNode.swift
+//  
+//
+//  Created by Siddharth Atre on 3/15/16.
+//
+//
+
+import Foundation
+
+/**
+ This class represents a node in the Ternary Search Tree. 
+ A node has two main data members, the key and the data. 
+ All nodes in a TST must have keys, but only some will have data.
+ This can be seen in the way the data variable is of Optional type.
+*/
+class TSTNode<Element> {
+    //Member properties of a particular node.
+    
+    /// The key that identifies this node.
+    var key: Character
+    /// The data stored in this node. May be `nil`
+    var data: Element?
+    /// Boolean flag to depict whether this node holds data or not.
+    var hasData: Bool
+    
+    /// The children of this node
+    var left: TSTNode?, right: TSTNode?, middle: TSTNode?
+    
+    /**
+     Initializer for key and/or data
+     
+     - parameter key:  The key to set for this node.
+     - parameter data: The optional data to set in this node.
+     */
+    init(key: Character, data: Element?) {
+        self.key = key
+        self.data = data
+        self.hasData = (data != nil)
+    }
+    
+    /**
+     Make a node that only has a key
+    
+     - parameter key: The key to ascribe to this node.
+     */
+    init(key:Character) {
+        self.key = key
+        self.data = nil
+        self.hasData = false
+    }
+    
+}