updated readme

Author: Kevin Taniguchi

Boyer-Moore/BoyerMoore.playground/Contents.swift

@@ -39,14 +39,10 @@ extension String {
   }
 }
 
-
 // A few simple tests
 
 let s = "Hello, World"
 s.indexOf(pattern: "World")  // 7
 
 let animals = "🐶🐔🐷🐮🐱"
 animals.indexOf(pattern: "🐮")  // 6
-
-
-

Boyer-Moore/BoyerMoore.playground/timeline.xctimeline

@@ -3,17 +3,17 @@
    version = "3.0">
    <TimelineItems>
       <LoggerValueHistoryTimelineItem
-         documentLocation = "#CharacterRangeLen=1&amp;CharacterRangeLoc=345&amp;EndingColumnNumber=37&amp;EndingLineNumber=9&amp;StartingColumnNumber=9&amp;StartingLineNumber=9&amp;Timestamp=497583231.982889"
+         documentLocation = "#CharacterRangeLen=1&amp;CharacterRangeLoc=345&amp;EndingColumnNumber=37&amp;EndingLineNumber=9&amp;StartingColumnNumber=9&amp;StartingLineNumber=9&amp;Timestamp=497585369.829471"
          selectedRepresentationIndex = "0"
          shouldTrackSuperviewWidth = "NO">
       </LoggerValueHistoryTimelineItem>
       <LoggerValueHistoryTimelineItem
-         documentLocation = "#CharacterRangeLen=0&amp;CharacterRangeLoc=345&amp;EndingColumnNumber=26&amp;EndingLineNumber=9&amp;StartingColumnNumber=9&amp;StartingLineNumber=9&amp;Timestamp=497583231.983042"
+         documentLocation = "#CharacterRangeLen=0&amp;CharacterRangeLoc=345&amp;EndingColumnNumber=26&amp;EndingLineNumber=9&amp;StartingColumnNumber=9&amp;StartingLineNumber=9&amp;Timestamp=497585369.82964"
          selectedRepresentationIndex = "0"
          shouldTrackSuperviewWidth = "NO">
       </LoggerValueHistoryTimelineItem>
       <LoggerValueHistoryTimelineItem
-         documentLocation = "#CharacterRangeLen=1&amp;CharacterRangeLoc=345&amp;EndingColumnNumber=25&amp;EndingLineNumber=9&amp;StartingColumnNumber=9&amp;StartingLineNumber=9&amp;Timestamp=497583231.983159"
+         documentLocation = "#CharacterRangeLen=1&amp;CharacterRangeLoc=345&amp;EndingColumnNumber=25&amp;EndingLineNumber=9&amp;StartingColumnNumber=9&amp;StartingLineNumber=9&amp;Timestamp=497585369.82978"
          selectedRepresentationIndex = "0"
          shouldTrackSuperviewWidth = "NO">
       </LoggerValueHistoryTimelineItem>

Boyer-Moore/README.markdown

@@ -150,34 +150,42 @@ Here's an implementation of the Boyer-Moore-Horspool algorithm:
 
 ```swift
 extension String {
-  public func indexOf(pattern: String) -> String.Index? {
+    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.dropLast().enumerate() {
-      skipTable[c] = patternLength - i - 1
+    for (i, c) in pattern.characters.enumerated() {
+    skipTable[c] = patternLength - i - 1
     }
 
-    var index = self.startIndex.advancedBy(patternLength - 1)
-
-    while index < self.endIndex {
-      var i = index
-      var p = pattern.endIndex.predecessor()
-
-      while self[i] == pattern[p] {
-        if p == pattern.startIndex { return i }
-        i = i.predecessor()
-        p = p.predecessor()
-      }
+    let p = pattern.index(before: pattern.endIndex)
+    let lastChar = pattern[p]
+    var i = self.index(startIndex, offsetBy: patternLength - 1)
 
-      let advance = skipTable[self[index]] ?? patternLength
-      index = index.advancedBy(advance)
+    func backwards() -> String.Index? {
+    var q = p
+    var j = i
+    while q > pattern.startIndex {
+    j = index(before: j)
+    q = index(before: q)
+    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 = index(after: i)
+    } else {
+    i = index(i, offsetBy: skipTable[c] ?? patternLength)
+    }
+    }
     return nil
-  }
+    }
 }
 ```