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Merged
merged 3 commits into from
Oct 7, 2017
Merged

Convex hull sometimes produces incorrect result 487 #630

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a47ddd7
fix: convex hull no longer produces concave shapes
mnespor Oct 7, 2017
dad8415
test: configure convex hull tests for travis ci
mnespor Oct 7, 2017
6d816c2
specify simulator for convex hull tests on travis
mnespor Oct 7, 2017
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1 change: 1 addition & 0 deletions .travis.yml
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Expand Up @@ -20,6 +20,7 @@ script:
- 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 ./Convex\ Hull/Convex\ Hull.xcodeproj -scheme Tests -destination 'platform=iOS Simulator,name=iPhone 7,OS=11.0'
- 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
Expand Down
146 changes: 145 additions & 1 deletion Convex Hull/Convex Hull.xcodeproj/project.pbxproj
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Expand Up @@ -7,13 +7,28 @@
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Expand All @@ -23,6 +38,13 @@
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Expand All @@ -33,10 +55,20 @@
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Expand All @@ -45,6 +77,7 @@
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Expand All @@ -64,6 +97,24 @@
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Expand All @@ -87,10 +138,15 @@
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Expand All @@ -112,11 +168,19 @@
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Expand All @@ -129,6 +193,15 @@
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Expand All @@ -140,6 +213,14 @@
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Expand All @@ -152,6 +233,60 @@
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Expand Down Expand Up @@ -274,6 +409,15 @@
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isa = XCConfigurationList;
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Expand Down
58 changes: 58 additions & 0 deletions Convex Hull/Convex Hull.xcodeproj/xcshareddata/xcschemes/Tests.xcscheme
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@@ -0,0 +1,58 @@
<?xml version="1.0" encoding="UTF-8"?>
<Scheme
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version = "1.3">
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<TestAction
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selectedDebuggerIdentifier = "Xcode.DebuggerFoundation.Debugger.LLDB"
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language = ""
shouldUseLaunchSchemeArgsEnv = "YES">
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BlueprintIdentifier = "1CB6142C1F89456C00A14493"
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ReferencedContainer = "container:Convex Hull.xcodeproj">
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</Testables>
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30 changes: 17 additions & 13 deletions Convex Hull/Convex Hull/View.swift
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Expand Up @@ -93,23 +93,11 @@ class View: UIView {
}

var pts = points

// calculate parameters of general line equation y = a * x + b
let a = (p1.y - p2.y) / (p1.x - p2.x)
let b = p1.y - a * p1.x

// calculate normal line's growth factor
let a1 = -1 / a

var maxDist: CGFloat = -1
var maxPoint: CGPoint = pts.first!

for p in pts { // for every point check the distance from our line
let b1 = p.y - a1 * p.x // calculate offset to line equation for given point p
let x = -(b - b1)/(a - a1) // calculate x where the two lines intersect
let y = a * x + b // calculate y value of this intersect point

let dist = pow(x - p.x, 2) + pow(y - p.y, 2) // calculate distance squared between intersection point and point p
let dist = distance(from: p, to: (p1, p2))
if dist > maxDist { // if distance is larger than current maxDist remember new point p
maxDist = dist
maxPoint = p
Expand Down Expand Up @@ -150,6 +138,22 @@ class View: UIView {
findHull(s2, maxPoint, p2)
}

func distance(from p: CGPoint, to line: (CGPoint, CGPoint)) -> CGFloat {
// If line.0 and line.1 are the same point, they don't define a line (and, besides,
// would cause division by zero in the distance formula). Return the distance between
// line.0 and point p instead.
if line.0 == line.1 {
return sqrt(pow(p.x - line.0.x, 2) + pow(p.y - line.0.y, 2))
}

// from Deza, Michel Marie; Deza, Elena (2013), Encyclopedia of Distances (2nd ed.), Springer, p. 86, ISBN 9783642309588
return abs((line.1.y - line.0.y) * p.x
- (line.1.x - line.0.x) * p.y
+ line.1.x * line.0.y
- line.1.y * line.0.x)
/ sqrt(pow(line.1.y - line.0.y, 2) + pow(line.1.x - line.0.x, 2))
}

override func draw(_ rect: CGRect) {

let context = UIGraphicsGetCurrentContext()
Expand Down
22 changes: 22 additions & 0 deletions Convex Hull/Tests/Info.plist
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@@ -0,0 +1,22 @@
<?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">
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<dict>
<key>CFBundleDevelopmentRegion</key>
<string>$(DEVELOPMENT_LANGUAGE)</string>
<key>CFBundleExecutable</key>
<string>$(EXECUTABLE_NAME)</string>
<key>CFBundleIdentifier</key>
<string>$(PRODUCT_BUNDLE_IDENTIFIER)</string>
<key>CFBundleInfoDictionaryVersion</key>
<string>6.0</string>
<key>CFBundleName</key>
<string>$(PRODUCT_NAME)</string>
<key>CFBundlePackageType</key>
<string>BNDL</string>
<key>CFBundleShortVersionString</key>
<string>1.0</string>
<key>CFBundleVersion</key>
<string>1</string>
</dict>
</plist>
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