Merge pull request #586 from vuinguyen/QuadTree-Swift4

[Swift 4] Update QuadTree

Author: kelvinlauKL

QuadTree/QuadTree.playground/Contents.swift

@@ -1,3 +1,8 @@
+// last checked with Xcode 9.0b5
+#if swift(>=4.0)
+print("Hello, Swift 4!")
+#endif
+
 import Foundation
 
 let tree = QuadTree(rect: Rect(origin: Point(0, 0), size: Size(xLength: 10, yLength: 10)))

QuadTree/README.md

@@ -152,7 +152,7 @@ Both adding a point and searching can still take up to O(n) in the worst case, s
 
 ### See also
 
-Displaying a large amount of objects in a MapView - a great use case for a Quadtree ([Thoughtbot Atricle](https://robots.thoughtbot.com/how-to-handle-large-amounts-of-data-on-maps))
+Displaying a large amount of objects in a MapView - a great use case for a Quadtree ([Thoughtbot Article](https://robots.thoughtbot.com/how-to-handle-large-amounts-of-data-on-maps))
 
 More info on [Wiki](https://en.wikipedia.org/wiki/Quadtree)