Array Jumping

You are given an integer array A of size N. You can jump from index J to index K, such that K > J, in the following way:

during odd-numbered jumps (i.e. jumps 1, 3, 5 and so on), you jump to the smallest index K such that A[J] < A[K] and A[K] − A[J] is minimal among all possible K's.
during even-numbered jumps (i.e. jumps 2, 4, 6 and so on), you jump to the smallest index K such that A[J] > A[K] and A[J] − A[K] is minimal among all possible K's.

It may be that, for some index J, there is no legal jump. In this case the jumping stops.

Write a function that, given an integer array A of length N, returns an integer denoting the number of starting points from which you can reach (maybe by jumping more than once) the end of the array A (index N − 1).

A = [10, 13, 12, 14, 15]
Answer: [14,15]