Merge pull request #1 from raywenderlich/master

update

Author: tangzzz-fan

.github/CONTRIBUTING.md

@@ -4,7 +4,9 @@ Want to help out with the Swift Algorithm Club? Great! While we don't have stric
 
 **Readability**
 
-The `README` file is the cake, and the sample code is the cherry on top. Readablity is really important for us. A good contribution has succinct explanations supported by diagrams. Code is best introduced in chunks, weaved into the explanations where relevant. 
+Our repo is all about learning. The `README` file is the cake, and the sample code is the cherry on top. A good contribution has succinct explanations supported by diagrams. Code is best introduced in chunks, weaved into the explanations where relevant. 
+
+> When choosing between brevity and performance, err to the side of brevity as long as the time complexity of the particular implementation is the same. You can make a note afterwards suggesting a more performant way of doing things. 
 
 **API Design Guidelines**
 
@@ -20,7 +22,7 @@ We follow the following Swift [style guide](https://github.com/raywenderlich/swi
 
 Unit tests. Fixes for typos. No contribution is too small. :-)
 
-The repository has over 100 different data structures and algorithms. We're always interested in improvements to existing implementations and better explanations. Suggestions for making the code more Swift-like or to make it fit better with the standard library is most welcomed. 
+The repository has over 100 different data structures and algorithms. We're always interested in improvements to existing implementations and better explanations. Suggestions for making the code more Swift-like or to make it fit better with the standard library are most welcome.
 
 ### New Contributions
 

.github/ISSUE_TEMPLATE.md

@@ -1,13 +1,7 @@
-### Category
-
-- [ ] Bug
-- [ ] Feature Request
-- [ ] Question
-
 ### Brief Intro
 
 <!-- Describe the issue briefly.-->
 
 ### More Details
 
-<!-- If necessary, start off with the code snippet. Put the code in between ``` to format them into code blocks.-->
+<!-- If necessary, start off with the code snippet. Put the code in between ``` to format them into code blocks.-->

.travis.yml

@@ -4,44 +4,52 @@ osx_image: xcode9
 
 install:
 
+- gem install xcpretty-travis-formatter
 # - ./install_swiftlint.sh
 
 script:
 
-- xcodebuild test -project ./All-Pairs\ Shortest\ Paths/APSP/APSP.xcodeproj -scheme APSPTests
-- xcodebuild test -project ./Array2D/Tests/Tests.xcodeproj -scheme Tests
-- xcodebuild test -project ./AVL\ Tree/Tests/Tests.xcodeproj -scheme Tests
-- xcodebuild test -project ./Binary\ Search/Tests/Tests.xcodeproj -scheme Tests
-- xcodebuild test -project ./Boyer-Moore/Tests/Tests.xcodeproj -scheme Tests
-- xcodebuild test -project ./Binary\ Search\ Tree/Solution\ 1/Tests/Tests.xcodeproj -scheme Tests
-- xcodebuild test -project ./Bloom\ Filter/Tests/Tests.xcodeproj -scheme Tests
-- xcodebuild test -project ./Bounded\ Priority\ Queue/Tests/Tests.xcodeproj -scheme Tests
-- xcodebuild test -project ./Breadth-First\ Search/Tests/Tests.xcodeproj -scheme Tests
-- xcodebuild test -project ./Bucket\ Sort/Tests/Tests.xcodeproj -scheme Tests
-- xcodebuild test -project ./B-Tree/Tests/Tests.xcodeproj -scheme Tests
-- xcodebuild test -project ./Comb\ Sort/Tests/Tests.xcodeproj -scheme Tests
-- xcodebuild test -project ./Counting\ Sort/Tests/Tests.xcodeproj -scheme Tests
-- xcodebuild test -project ./Depth-First\ Search/Tests/Tests.xcodeproj -scheme Tests
-- xcodebuild test -project ./Graph/Graph.xcodeproj -scheme GraphTests
-- xcodebuild test -project ./Heap/Tests/Tests.xcodeproj -scheme Tests
-- xcodebuild test -project ./Heap\ Sort/Tests/Tests.xcodeproj -scheme Tests
-- xcodebuild test -project ./Insertion\ Sort/Tests/Tests.xcodeproj -scheme Tests
-- xcodebuild test -project ./K-Means/Tests/Tests.xcodeproj -scheme Tests
-- xcodebuild test -project ./Linked\ List/Tests/Tests.xcodeproj -scheme Tests
-- xcodebuild test -project ./Longest\ Common\ Subsequence/Tests/Tests.xcodeproj -scheme Tests
-- xcodebuild test -project ./Minimum\ Spanning\ Tree\ \(Unweighted\)/Tests/Tests.xcodeproj -scheme Tests
-- xcodebuild test -project ./Priority\ Queue/Tests/Tests.xcodeproj -scheme Tests
-- xcodebuild test -project ./Queue/Tests/Tests.xcodeproj -scheme Tests
-- xcodebuild test -project ./Quicksort/Tests/Tests-Quicksort.xcodeproj -scheme Tests-Quicksort
-- xcodebuild test -project ./Radix\ Sort/Tests/Tests.xcodeproj -scheme Tests
-- xcodebuild test -project ./Rootish\ Array\ Stack/Tests/Tests.xcodeproj -scheme Tests
-- xcodebuild test -project ./Select\ Minimum\ Maximum/Tests/Tests.xcodeproj -scheme Tests
-- xcodebuild test -project ./Selection\ Sort/Tests/Tests.xcodeproj -scheme Tests
-- xcodebuild test -project ./Shell\ Sort/Tests/Tests.xcodeproj -scheme Tests
-- xcodebuild test -project ./Shortest\ Path\ \(Unweighted\)/Tests/Tests.xcodeproj -scheme Tests
-- xcodebuild test -project ./Single-Source\ Shortest\ Paths\ \(Weighted\)/SSSP.xcodeproj -scheme SSSPTests
-- xcodebuild test -project ./Stack/Tests/Tests.xcodeproj -scheme Tests
-- xcodebuild test -project ./Topological\ Sort/Tests/Tests.xcodeproj -scheme Tests
-- xcodebuild test -project ./Treap/Treap/Treap.xcodeproj -scheme Tests
-- xcodebuild test -project ./Palindromes/Test/Test.xcodeproj -scheme Test
-- xcodebuild test -project ./Ternary\ Search\ Tree/Tests/Tests.xcodeproj -scheme Tests
+- xcodebuild test -project ./Array2D/Tests/Tests.xcodeproj -scheme Tests | xcpretty -f `xcpretty-travis-formatter`
+- xcodebuild test -project ./All-Pairs\ Shortest\ Paths/APSP/APSP.xcodeproj -scheme APSPTests | xcpretty -f `xcpretty-travis-formatter`
+- xcodebuild test -project ./AVL\ Tree/Tests/Tests.xcodeproj -scheme Tests | xcpretty -f `xcpretty-travis-formatter`
+- xcodebuild test -project ./Binary\ Search/Tests/Tests.xcodeproj -scheme Tests | xcpretty -f `xcpretty-travis-formatter`
+- xcodebuild test -project ./Boyer-Moore-Horspool/Tests/Tests.xcodeproj -scheme Tests | xcpretty -f `xcpretty-travis-formatter`
+- xcodebuild test -project ./Binary\ Search\ Tree/Solution\ 1/Tests/Tests.xcodeproj -scheme Tests | xcpretty -f `xcpretty-travis-formatter`
+- xcodebuild test -project ./Bloom\ Filter/Tests/Tests.xcodeproj -scheme Tests | xcpretty -f `xcpretty-travis-formatter`
+- xcodebuild test -project ./Bounded\ Priority\ Queue/Tests/Tests.xcodeproj -scheme Tests | xcpretty -f `xcpretty-travis-formatter`
+- xcodebuild test -project ./Breadth-First\ Search/Tests/Tests.xcodeproj -scheme Tests | xcpretty -f `xcpretty-travis-formatter`
+- xcodebuild test -project ./Bucket\ Sort/Tests/Tests.xcodeproj -scheme Tests | xcpretty -f `xcpretty-travis-formatter`
+- xcodebuild test -project ./B-Tree/Tests/Tests.xcodeproj -scheme Tests | xcpretty -f `xcpretty-travis-formatter`
+- xcodebuild test -project ./Comb\ Sort/Tests/Tests.xcodeproj -scheme Tests | xcpretty -f `xcpretty-travis-formatter`
+- xcodebuild test -project ./Convex\ Hull/Convex\ Hull.xcodeproj -scheme Tests -destination 'platform=iOS Simulator,name=iPhone 7,OS=11.0' | xcpretty -f `xcpretty-travis-formatter`
+- xcodebuild test -project ./Counting\ Sort/Tests/Tests.xcodeproj -scheme Tests | xcpretty -f `xcpretty-travis-formatter`
+- xcodebuild test -project ./Depth-First\ Search/Tests/Tests.xcodeproj -scheme Tests | xcpretty -f `xcpretty-travis-formatter`
+- xcodebuild test -project ./Graph/Graph.xcodeproj -scheme GraphTests | xcpretty -f `xcpretty-travis-formatter`
+- xcodebuild test -project ./Heap/Tests/Tests.xcodeproj -scheme Tests | xcpretty -f `xcpretty-travis-formatter`
+- xcodebuild test -project ./Heap\ Sort/Tests/Tests.xcodeproj -scheme Tests | xcpretty -f `xcpretty-travis-formatter`
+- xcodebuild test -project ./Insertion\ Sort/Tests/Tests.xcodeproj -scheme Tests | xcpretty -f `xcpretty-travis-formatter`
+- xcodebuild test -project ./K-Means/Tests/Tests.xcodeproj -scheme Tests | xcpretty -f `xcpretty-travis-formatter`
+- xcodebuild test -project ./Linked\ List/Tests/Tests.xcodeproj -scheme Tests | xcpretty -f `xcpretty-travis-formatter`
+- xcodebuild test -project ./Singly\ Linked\ List/Tests/Tests.xcodeproj -scheme Tests | xcpretty -f `xcpretty-travis-formatter`
+- xcodebuild test -project ./Longest\ Common\ Subsequence/Tests/Tests.xcodeproj -scheme Tests | xcpretty -f `xcpretty-travis-formatter`
+- xcodebuild test -project ./Minimum\ Spanning\ Tree\ \(Unweighted\)/Tests/Tests.xcodeproj -scheme Tests | xcpretty -f `xcpretty-travis-formatter`
+- xcodebuild test -project ./Priority\ Queue/Tests/Tests.xcodeproj -scheme Tests | xcpretty -f `xcpretty-travis-formatter`
+- xcodebuild test -project ./Queue/Tests/Tests.xcodeproj -scheme Tests | xcpretty -f `xcpretty-travis-formatter`
+- xcodebuild test -project ./Quicksort/Tests/Tests-Quicksort.xcodeproj -scheme Test-Quicksort | xcpretty -f `xcpretty-travis-formatter`
+- xcodebuild test -project ./Radix\ Sort/Tests/Tests.xcodeproj -scheme Tests | xcpretty -f `xcpretty-travis-formatter`
+- xcodebuild test -project ./Rootish\ Array\ Stack/Tests/Tests.xcodeproj -scheme Tests | xcpretty -f `xcpretty-travis-formatter`
+- xcodebuild test -project ./Select\ Minimum\ Maximum/Tests/Tests.xcodeproj -scheme Tests | xcpretty -f `xcpretty-travis-formatter`
+- xcodebuild test -project ./Selection\ Sort/Tests/Tests.xcodeproj -scheme Tests | xcpretty -f `xcpretty-travis-formatter`
+- xcodebuild test -project ./Shell\ Sort/Tests/Tests.xcodeproj -scheme Tests | xcpretty -f `xcpretty-travis-formatter`
+- xcodebuild test -project ./Shortest\ Path\ \(Unweighted\)/Tests/Tests.xcodeproj -scheme Tests | xcpretty -f `xcpretty-travis-formatter`
+- xcodebuild test -project ./Single-Source\ Shortest\ Paths\ \(Weighted\)/SSSP.xcodeproj -scheme SSSPTests | xcpretty -f `xcpretty-travis-formatter`
+- xcodebuild test -project ./Stack/Tests/Tests.xcodeproj -scheme Tests | xcpretty -f `xcpretty-travis-formatter`
+- xcodebuild test -project ./Topological\ Sort/Tests/Tests.xcodeproj -scheme Tests | xcpretty -f `xcpretty-travis-formatter`
+- xcodebuild test -project ./Treap/Treap/Treap.xcodeproj -scheme Tests | xcpretty -f `xcpretty-travis-formatter`
+- xcodebuild test -project ./Palindromes/Test/Test.xcodeproj -scheme Test | xcpretty -f `xcpretty-travis-formatter`
+- xcodebuild test -project ./Ternary\ Search\ Tree/Tests/Tests.xcodeproj -scheme Tests | xcpretty -f `xcpretty-travis-formatter`
+- xcodebuild test -project ./Karatsuba\ Multiplication/Tests/Tests.xcodeproj -scheme Tests | xcpretty -f `xcpretty-travis-formatter`
+
+after_success:
+
+- if [[ "$TRAVIS_BRANCH" == "master" ]]; then ./gfm-render.sh; fi

3Sum and 4Sum/3Sum.playground/Contents.swift

@@ -0,0 +1,67 @@
+// last checked with Xcode 10.1
+#if swift(>=4.2)
+print("Hello, Swift 4.2!")
+#endif
+
+extension Collection where Element: Equatable {
+  
+  /// In a sorted collection, replaces the given index with a successor mapping to a unique element.
+  ///
+  /// - Parameter index: A valid index of the collection. `index` must be less than `endIndex`
+  func formUniqueIndex(after index: inout Index) {
+    var prev = index
+    repeat {
+      prev = index
+      formIndex(after: &index)
+    } while index < endIndex && self[prev] == self[index]
+  }
+}
+
+extension BidirectionalCollection where Element: Equatable {
+  
+  /// In a sorted collection, replaces the given index with a predecessor that maps to a unique element.
+  ///
+  /// - Parameter index: A valid index of the collection. `index` must be greater than `startIndex`.
+  func formUniqueIndex(before index: inout Index) {
+    var prev = index
+    repeat {
+      prev = index
+      formIndex(before: &index)
+    } while index > startIndex && self[prev] == self[index]
+  }
+}
+
+func threeSum<T: BidirectionalCollection>(_ collection: T, target: T.Element) -> [[T.Element]] where T.Element: Numeric & Comparable {
+  let sorted = collection.sorted()
+  var ret: [[T.Element]] = []
+  var l = sorted.startIndex
+  
+  ThreeSum: while l < sorted.endIndex { defer { sorted.formUniqueIndex(after: &l) }
+    var m = sorted.index(after: l)
+    var r = sorted.index(before: sorted.endIndex)
+    
+    TwoSum: while m < r && r < sorted.endIndex { 
+      let sum = sorted[l] + sorted[m] + sorted[r]
+      if sum == target {
+        ret.append([sorted[l], sorted[m], sorted[r]])
+        sorted.formUniqueIndex(after: &m)
+        sorted.formUniqueIndex(before: &r)
+      } else if sum < target {
+        sorted.formUniqueIndex(after: &m)
+      } else {
+        sorted.formUniqueIndex(before: &r)
+      }
+    }
+  }
+  
+  return ret
+}
+
+// Answer: [[-1, 0, 1], [-1, -1, 2]]
+threeSum([-1, 0, 1, 2, -1, -4], target: 0)
+
+// Answer: [[-1, -1, 2], [-1, 0, 1]]
+threeSum([-1, -1, -1, -1, 2, 1, -4, 0], target: 0)
+
+// Answer: [[-1, -1, 2]]
+threeSum([-1, -1, -1, -1, -1, -1, 2], target: 0)

Ordered Set/AppleOrderedSet.playground/contents.xcplayground renamed to 3Sum and 4Sum/3Sum.playground/contents.xcplayground

@@ -0,0 +1,8 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+<plist version="1.0">
+<dict>
+	<key>IDEDidComputeMac32BitWarning</key>
+	<true/>
+</dict>
+</plist>

Binary Search/BinarySearch.playground/playground.xcworkspace/contents.xcworkspacedata renamed to 3Sum and 4Sum/3Sum.playground/playground.xcworkspace/contents.xcworkspacedata

@@ -0,0 +1,64 @@
+// last checked with Xcode 10.1
+#if swift(>=4.2)
+print("Hello, Swift 4.2!")
+#endif
+
+extension Collection where Element: Equatable {
+  
+  /// In a sorted collection, replaces the given index with a successor mapping to a unique element.
+  ///
+  /// - Parameter index: A valid index of the collection. `index` must be less than `endIndex`
+  func formUniqueIndex(after index: inout Index) {
+    var prev = index
+    repeat {
+      prev = index
+      formIndex(after: &index)
+    } while index < endIndex && self[prev] == self[index]
+  }
+}
+
+extension BidirectionalCollection where Element: Equatable {
+  
+  /// In a sorted collection, replaces the given index with a predecessor that maps to a unique element.
+  ///
+  /// - Parameter index: A valid index of the collection. `index` must be greater than `startIndex`.
+  func formUniqueIndex(before index: inout Index) {
+    var prev = index
+    repeat {
+      prev = index
+      formIndex(before: &index)
+    } while index > startIndex && self[prev] == self[index]
+  }
+}
+
+func fourSum<T: BidirectionalCollection>(_ collection: T, target: T.Element) -> [[T.Element]] where T.Element: Numeric & Comparable {
+  let sorted = collection.sorted()
+  var ret: [[T.Element]] = []
+  
+  var l = sorted.startIndex
+  FourSum: while l < sorted.endIndex { defer { sorted.formUniqueIndex(after: &l) }
+    var ml = sorted.index(after: l)
+                                      
+    ThreeSum: while ml < sorted.endIndex { defer { sorted.formUniqueIndex(after: &ml) }
+      var mr = sorted.index(after: ml)
+      var r = sorted.index(before: sorted.endIndex)
+      
+      TwoSum: while mr < r && r < sorted.endIndex {
+        let sum = sorted[l] + sorted[ml] + sorted[mr] + sorted[r]
+        if sum == target {
+          ret.append([sorted[l], sorted[ml], sorted[mr], sorted[r]])
+          sorted.formUniqueIndex(after: &mr)
+          sorted.formUniqueIndex(before: &r)
+        } else if sum < target {
+          sorted.formUniqueIndex(after: &mr)
+        } else {
+          sorted.formUniqueIndex(before: &r)
+        }
+      }
+    }
+  }
+  return ret
+}
+
+// answer: [[-2, -1, 1, 2], [-2, 0, 0, 2], [-1, 0, 0, 1]]
+fourSum([1, 0, -1, 0, -2, 2], target: 0)

3Sum and 4Sum/3Sum.playground/playground.xcworkspace/xcshareddata/IDEWorkspaceChecks.plist

@@ -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>