Merge pull request kodecocodes#499 from remlostime/decode-tree

Encode and Decode A Binary Tree

Encode and Decode Tree/EncodeAndDecodeTree.playground/Contents.swift

@@ -0,0 +1,46 @@
+//: Playground - noun: a place where people can play
+
+func printTree(_ root: BinaryNode<String>?) {
+    guard let root = root else {
+        return
+    }
+
+    let leftVal = root.left == nil ? "nil" : root.left!.val
+    let rightVal = root.right == nil ? "nil" : root.right!.val
+
+    print("val: \(root.val) left: \(leftVal) right: \(rightVal)")
+
+    printTree(root.left)
+    printTree(root.right)
+}
+
+let coder = BinaryNodeCoder<String>()
+
+let node1 = BinaryNode("a")
+let node2 = BinaryNode("b")
+let node3 = BinaryNode("c")
+let node4 = BinaryNode("d")
+let node5 = BinaryNode("e")
+
+node1.left = node2
+node1.right = node3
+node3.left = node4
+node3.right = node5
+
+let encodeStr = try coder.encode(node1)
+print(encodeStr)
+// "a b # # c d # # e # #"
+
+
+let root: BinaryNode<String> = coder.decode(from: encodeStr)!
+print("Tree:")
+printTree(root)
+/*
+ Tree:
+ val: a left: b right: c
+ val: b left: nil right: nil
+ val: c left: d right: e
+ val: d left: nil right: nil
+ val: e left: nil right: nil
+ */
+

Encode and Decode Tree/EncodeAndDecodeTree.playground/Sources/EncodeAndDecodeTree.swift

@@ -0,0 +1,95 @@
+//
+//  EncodeAndDecodeTree.swift
+//  
+//
+//  Created by Kai Chen on 19/07/2017.
+//
+//
+
+import Foundation
+
+protocol BinaryNodeEncoder {
+  func encode<T>(_ node: BinaryNode<T>?) throws -> String
+}
+
+protocol BinaryNodeDecoder {
+  func decode<T>(from string: String) -> BinaryNode<T>?
+}
+
+public class BinaryNodeCoder<T: Comparable>: BinaryNodeEncoder, BinaryNodeDecoder {
+
+  // MARK: Private
+
+  private let separator: Character = ","
+  private let nilNode = "X"
+
+  private func decode<T>(from array: inout [String]) -> BinaryNode<T>? {
+    guard !array.isEmpty else {
+      return nil
+    }
+
+    let value = array.removeLast()
+
+    guard value != nilNode, let val = value as? T else {
+      return nil
+    }
+
+    let node = BinaryNode<T>(val)
+    node.left = decode(from: &array)
+    node.right = decode(from: &array)
+
+    return node
+  }
+
+  // MARK: Public
+
+  public init() {}
+
+  public func encode<T>(_ node: BinaryNode<T>?) throws -> String {
+    var str = ""
+    node?.preOrderTraversal { data in
+      if let data = data {
+        let string = String(describing: data)
+        str.append(string)
+      } else {
+        str.append(nilNode)
+      }
+      str.append(separator)
+    }
+
+    return str
+  }
+
+  public func decode<T>(from string: String) -> BinaryNode<T>? {
+    var components = string.split(separator: separator).reversed().map(String.init)
+    return decode(from: &components)
+  }
+}
+
+public class BinaryNode<Element: Comparable> {
+  public var val: Element
+  public var left: BinaryNode?
+  public var right: BinaryNode?
+
+  public init(_ val: Element, left: BinaryNode? = nil, right: BinaryNode? = nil) {
+    self.val = val
+    self.left = left
+    self.right = right
+  }
+
+  public func preOrderTraversal(visit: (Element?) throws -> ()) rethrows {
+    try visit(val)
+
+    if let left = left {
+      try left.preOrderTraversal(visit: visit)
+    } else {
+      try visit(nil)
+    }
+
+    if let right = right {
+      try right.preOrderTraversal(visit: visit)
+    } else {
+      try visit(nil)
+    }
+  }
+}

Encode and Decode Tree/EncodeAndDecodeTree.playground/contents.xcplayground

@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+<playground version='5.0' target-platform='ios'>
+    <timeline fileName='timeline.xctimeline'/>
+</playground>

Encode and Decode Tree/EncodeAndDecodeTree.swift

@@ -0,0 +1,95 @@
+//
+//  EncodeAndDecodeTree.swift
+//
+//
+//  Created by Kai Chen on 19/07/2017.
+//
+//
+
+import Foundation
+
+protocol BinaryNodeEncoder {
+  func encode<T>(_ node: BinaryNode<T>?) throws -> String
+}
+
+protocol BinaryNodeDecoder {
+  func decode<T>(from string: String) -> BinaryNode<T>?
+}
+
+public class BinaryNodeCoder<T: Comparable>: BinaryNodeEncoder, BinaryNodeDecoder {
+
+  // MARK: Private
+
+  private let separator: Character = ","
+  private let nilNode = "X"
+
+  private func decode<T>(from array: inout [String]) -> BinaryNode<T>? {
+    guard !array.isEmpty else {
+      return nil
+    }
+
+    let value = array.removeLast()
+
+    guard value != nilNode, let val = value as? T else {
+      return nil
+    }
+
+    let node = BinaryNode<T>(val)
+    node.left = decode(from: &array)
+    node.right = decode(from: &array)
+
+    return node
+  }
+
+  // MARK: Public
+
+  public init() {}
+
+  public func encode<T>(_ node: BinaryNode<T>?) throws -> String {
+    var str = ""
+    node?.preOrderTraversal { data in
+      if let data = data {
+        let string = String(describing: data)
+        str.append(string)
+      } else {
+        str.append(nilNode)
+      }
+      str.append(separator)
+    }
+
+    return str
+  }
+
+  public func decode<T>(from string: String) -> BinaryNode<T>? {
+    var components = string.split(separator: separator).reversed().map(String.init)
+    return decode(from: &components)
+  }
+}
+
+public class BinaryNode<Element: Comparable> {
+  public var val: Element
+  public var left: BinaryNode?
+  public var right: BinaryNode?
+
+  public init(_ val: Element, left: BinaryNode? = nil, right: BinaryNode? = nil) {
+    self.val = val
+    self.left = left
+    self.right = right
+  }
+
+  public func preOrderTraversal(visit: (Element?) throws -> ()) rethrows {
+    try visit(val)
+
+    if let left = left {
+      try left.preOrderTraversal(visit: visit)
+    } else {
+      try visit(nil)
+    }
+
+    if let right = right {
+      try right.preOrderTraversal(visit: visit)
+    } else {
+      try visit(nil)
+    }
+  }
+}