Add hash set

Hash Set/HashSet.playground/Contents.swift

@@ -0,0 +1,118 @@
+//: Playground - noun: a place where people can play
+
+public struct HashSet<T: Hashable> {
+  private var dictionary = Dictionary<T, Bool>()
+
+  public mutating func insert(element: T) {
+    dictionary[element] = true
+  }
+
+  public mutating func remove(element: T) {
+    dictionary[element] = nil
+  }
+
+  public func contains(element: T) -> Bool {
+    return dictionary[element] != nil
+  }
+
+  public func allElements() -> [T] {
+    return Array(dictionary.keys)
+  }
+
+  public var count: Int {
+    return dictionary.count
+  }
+
+  public var isEmpty: Bool {
+    return dictionary.isEmpty
+  }
+}
+
+var set = HashSet<String>()
+
+set.insert("one")
+set.insert("two")
+set.insert("three")
+set.allElements()
+
+set.insert("two")
+set.allElements()
+
+set.contains("one")
+set.remove("one")
+set.allElements()
+set.contains("one")
+
+
+
+/* Union */
+
+extension HashSet {
+  public func union(otherSet: HashSet<T>) -> HashSet<T> {
+    var combined = HashSet<T>()
+    for obj in dictionary.keys {
+      combined.insert(obj)
+    }
+    for obj in otherSet.dictionary.keys {
+      combined.insert(obj)
+    }
+    return combined
+  }
+}
+
+
+var setA = HashSet<Int>()
+setA.insert(1)
+setA.insert(2)
+setA.insert(3)
+setA.insert(4)
+
+var setB = HashSet<Int>()
+setB.insert(3)
+setB.insert(4)
+setB.insert(5)
+setB.insert(6)
+
+let union = setA.union(setB)
+union.allElements()          // [5, 6, 2, 3, 1, 4]
+
+
+
+/* Intersection */
+
+extension HashSet {
+  public func intersect(otherSet: HashSet<T>) -> HashSet<T> {
+    var common = HashSet<T>()
+    for obj in dictionary.keys {
+      if otherSet.contains(obj) {
+        common.insert(obj)
+      }
+    }
+    return common
+  }
+}
+
+let intersection = setA.intersect(setB)
+intersection.allElements()               // [3, 4]
+
+
+
+/* Difference */
+
+extension HashSet {
+  public func difference(otherSet: HashSet<T>) -> HashSet<T> {
+    var diff = HashSet<T>()
+    for obj in dictionary.keys {
+      if !otherSet.contains(obj) {
+        diff.insert(obj)
+      }
+    }
+    return diff
+  }
+}
+
+let difference1 = setA.difference(setB)
+difference1.allElements()                // [2, 1]
+
+let difference2 = setB.difference(setA)
+difference2.allElements()                // [5, 6]

Hash Set/HashSet.playground/contents.xcplayground

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

Hash Set/HashSet.playground/timeline.xctimeline

@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<Timeline
+   version = "3.0">
+   <TimelineItems>
+   </TimelineItems>
+</Timeline>

Hash Set/HashSet.swift

@@ -0,0 +1,60 @@
+public struct HashSet<T: Hashable> {
+  private var dictionary = Dictionary<T, Bool>()
+
+  public mutating func insert(element: T) {
+    dictionary[element] = true
+  }
+
+  public mutating func remove(element: T) {
+    dictionary[element] = nil
+  }
+
+  public func contains(element: T) -> Bool {
+    return dictionary[element] != nil
+  }
+
+  public func allElements() -> [T] {
+    return Array(dictionary.keys)
+  }
+
+  public var count: Int {
+    return dictionary.count
+  }
+
+  public var isEmpty: Bool {
+    return dictionary.isEmpty
+  }
+}
+
+extension HashSet {
+  public func union(otherSet: HashSet<T>) -> HashSet<T> {
+    var combined = HashSet<T>()
+    for obj in dictionary.keys {
+      combined.insert(obj)
+    }
+    for obj in otherSet.dictionary.keys {
+      combined.insert(obj)
+    }
+    return combined
+  }
+
+  public func intersect(otherSet: HashSet<T>) -> HashSet<T> {
+    var common = HashSet<T>()
+    for obj in dictionary.keys {
+      if otherSet.contains(obj) {
+        common.insert(obj)
+      }
+    }
+    return common
+  }
+
+  public func difference(otherSet: HashSet<T>) -> HashSet<T> {
+    var diff = HashSet<T>()
+    for obj in dictionary.keys {
+      if !otherSet.contains(obj) {
+        diff.insert(obj)
+      }
+    }
+    return diff
+  }
+}