Add playgrounds where missing

Boyer-Moore/BoyerMoore.playground/Contents.swift

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+//: Playground - noun: a place where people can play
+
+extension String {
+  func indexOf(pattern: String) -> String.Index? {
+    let patternLength = pattern.characters.count
+    assert(patternLength > 0)
+    assert(patternLength <= self.characters.count)
+
+    var skipTable = [Character: Int]()
+    for (i, c) in pattern.characters.enumerate() {
+      skipTable[c] = patternLength - i - 1
+    }
+
+    let p = pattern.endIndex.predecessor()
+    let lastChar = pattern[p]
+    var i = self.startIndex.advancedBy(patternLength - 1)
+
+    func backwards() -> String.Index? {
+      var q = p
+      var j = i
+      while q > pattern.startIndex {
+        j = j.predecessor()
+        q = q.predecessor()
+        if self[j] != pattern[q] { return nil }
+      }
+      return j
+    }
+
+    while i < self.endIndex {
+      let c = self[i]
+      if c == lastChar {
+        if let k = backwards() { return k }
+        i = i.successor()
+      } else {
+        i = i.advancedBy(skipTable[c] ?? patternLength)
+      }
+    }
+    return nil
+  }
+}
+
+// A few simple tests
+
+let s = "Hello, World"
+s.indexOf("World")  // 7
+
+// Input:
+let animals = "🐶🐔🐷🐮🐱"
+animals.indexOf("🐮")  // 6

Boyer-Moore/BoyerMoore.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>

Boyer-Moore/BoyerMoore.playground/timeline.xctimeline

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

Insertion Sort/InsertionSort.playground/Contents.swift

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+//: Playground - noun: a place where people can play
+
+func insertionSort<T>(array: [T], _ isOrderedBefore: (T, T) -> Bool) -> [T] {
+  var a = array
+  for x in 1..<a.count {
+    var y = x
+    let temp = a[y]
+    while y > 0 && isOrderedBefore(temp, a[y - 1]) {
+      a[y] = a[y - 1]
+      y -= 1
+    }
+    a[y] = temp
+  }
+  return a
+}
+
+let list = [ 10, -1, 3, 9, 2, 27, 8, 5, 1, 3, 0, 26 ]
+insertionSort(list, <)
+insertionSort(list, >)

Insertion Sort/InsertionSort.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>

Insertion Sort/InsertionSort.playground/timeline.xctimeline

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

Selection Sort/SelectionSort.playground/Contents.swift

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+//: Playground - noun: a place where people can play
+
+func selectionSort<T>(array: [T], _ isOrderedBefore: (T, T) -> Bool) -> [T] {
+  guard array.count > 1 else { return array }
+  var a = array
+  for x in 0 ..< a.count - 1 {
+    var lowest = x
+    for y in x + 1 ..< a.count {
+      if isOrderedBefore(a[y], a[lowest]) {
+        lowest = y
+      }
+    }
+    if x != lowest {
+      swap(&a[x], &a[lowest])
+    }
+  }
+  return a
+}
+
+let list = [ 10, -1, 3, 9, 2, 27, 8, 5, 1, 3, 0, 26 ]
+selectionSort(list, <)
+selectionSort(list, >)

Selection Sort/SelectionSort.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>

Selection Sort/SelectionSort.playground/timeline.xctimeline

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

Two-Sum Problem/2Sum.playground/Contents.swift

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+//: Playground - noun: a place where people can play
+
+func twoSumProblem(a: [Int], k: Int) -> ((Int, Int))? {
+  var i = 0
+  var j = a.count - 1
+
+  while i < j {
+    let sum = a[i] + a[j]
+    if sum == k {
+      return (i, j)
+    } else if sum < k {
+      ++i
+    } else {
+      --j
+    }
+  }
+  return nil
+}
+
+let a = [2, 3, 4, 4, 7, 8, 9, 10, 12, 14, 21, 22, 100]
+if let (i, j) = twoSumProblem(a, k: 33) {
+  i            // 8
+  a[i]         // 12
+  j            // 10
+  a[j]         // 21
+  a[i] + a[j]  // 33
+}
+
+twoSumProblem(a, k: 37)  // nil

Two-Sum Problem/2Sum.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>

Two-Sum Problem/2Sum.playground/timeline.xctimeline

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