Binary Search — Minimum in a Rotated Sorted Array

solve(nums) — nums was sorted ascending with distinct values, then rotated an
unknown number of times ([0,1,2,4,5,6,7] can become [4,5,6,7,0,1,2]). Return the
smallest value in O(log n).

Compare nums[mid] to the last element, not the first: if nums[mid] > nums[hi]
the drop (and the minimum) is on the right of mid; otherwise the minimum is at mid
or on its left.

Examples

solve([3,4,5,1,2])        → 1
solve([4,5,6,7,0,1,2])    → 0
solve([11,13,15,17])      → 11     // rotated n times = not rotated