500px/PSTCollectionView — pull request #2 by tapi (2012-10-11 21:45:40+00:00)
Title: Improved implementation of indexPathsForVisibleItems

Existing implementation iterated over the result from visibleCells and then called indexPathForCell for each cell both of which iterated over the _allVisibleViewsDict giving us a runtime of O(n^2)

new implementation just iterates over _allVisibleViewsDict like the methods of similar nature