Remove Binary Search

[jjatie]

• [ x] I've read, understood, and done my best to follow the *CONTRIBUTING guidelines.

Background

Binary search provides optimized search for sorted collections. For unsorted collections, binary search is significantly slower than iterating over the collection. Charts implements binary search, however it does not enforce sorted collections, causing significantly slower lookup times for unsorted collections.

Proposal

Remove binary search until such a time that we can a) enforce sorted chart data or b) have sorted and unsorted chart data with different look up algorithms.

Charts Environment

**Charts version: 3.2
**Xcode version:10
**Swift version:4.2

[liuxuan30]

I remember it's sorted back in time. You sure we are binary searching unsorted collections? Did we change it to unsorted by mistake?

[jjatie]

@liuxuan30 Yes, we perform binary search on all sets with no guarantee they are sorted.

[liuxuan30]

If so, we indeed need to fix. But I guess the search will have high false rate? I wonder why no people complain about this. especially when highlighting.