Added directory for all files.

Author: mrael2

Set Cover (Unweighted)/README.markdown

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+import Foundation
+
+public func randomArrayOfSets<T>(covering universe: Set<T>,
+                              minArraySizeFactor: Double = 0.8,
+                              maxSetSizeFactor: Double = 0.6) -> Array<Set<T>> {
+  var result = [Set<T>]()
+  var ongoingUnion = Set<T>()
+  
+  let minArraySize = Int(Double(universe.count) * minArraySizeFactor)
+  var maxSetSize = Int(Double(universe.count) * maxSetSizeFactor)
+  if maxSetSize > universe.count {
+    maxSetSize = universe.count
+  }
+  
+  while true {
+    var generatedSet = Set<T>()
+    let targetSetSize = Int(arc4random_uniform(UInt32(maxSetSize)) + 1)
+    
+    while true {
+      let randomUniverseIndex = Int(arc4random_uniform(UInt32(universe.count)))
+      for (setIndex, value) in universe.enumerate() {
+        if setIndex == randomUniverseIndex {
+          generatedSet.insert(value)
+          break
+        }
+      }
+      
+      if generatedSet.count == targetSetSize {
+        result.append(generatedSet)
+        ongoingUnion = ongoingUnion.union(generatedSet)
+        break
+      }
+    }
+    
+    if result.count >= minArraySize {
+      if ongoingUnion == universe {
+        break
+      }
+    }
+  }
+  
+  return result
+}

SetCover.playground/Contents.swift renamed to Set Cover (Unweighted)/SetCover.playground/Contents.swift

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+public extension Set {
+  func cover(from array: Array<Set<Element>>) -> Array<Set<Element>>? {
+    var result: [Set<Element>]? = [Set<Element>]()
+    var remainingSet = self
+    
+    func largestIntersectingSet() -> Set<Element>? {
+      var largestIntersectionLength = 0
+      var largestSet: Set<Element>?
+      
+      for set in array {
+        let intersectionLength = remainingSet.intersect(set).count
+        if intersectionLength > largestIntersectionLength {
+          largestIntersectionLength = intersectionLength
+          largestSet = set
+        }
+      }
+      
+      return largestSet
+    }
+    
+    while remainingSet.count != 0 {
+      guard let largestSet = largestIntersectingSet() else { break }
+      result!.append(largestSet)
+      remainingSet = remainingSet.subtract(largestSet)
+    }
+    
+    if remainingSet.count != 0 || self.count == 0 {
+      result = nil
+    }
+    
+    return result
+  }
+}

Set Cover (Unweighted)/SetCover.playground/Sources/RandomArrayOfSets.swift

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+extension Set {
+  func cover(from array: Array<Set<Element>>) -> Array<Set<Element>>? {
+    var result: [Set<Element>]? = [Set<Element>]()
+    var remainingSet = self
+    
+    func largestIntersectingSet() -> Set<Element>? {
+      var largestIntersectionLength = 0
+      var largestSet: Set<Element>?
+      
+      for set in array {
+        let intersectionLength = remainingSet.intersect(set).count
+        if intersectionLength > largestIntersectionLength {
+          largestIntersectionLength = intersectionLength
+          largestSet = set
+        }
+      }
+      
+      return largestSet
+    }
+    
+    while remainingSet.count != 0 {
+      guard let largestSet = largestIntersectingSet() else { break }
+      result!.append(largestSet)
+      remainingSet = remainingSet.subtract(largestSet)
+    }
+    
+    if remainingSet.count != 0 || self.count == 0 {
+      result = nil
+    }
+    
+    return result
+  }
+}