#SubArrMinAvg Find the starting Index of sub-array with minimal Average.
Assume that:
N is an integer within the range [2..100,000]; each element of array A is an integer within the range [โ10,000..10,000]. Complexity:
expected worst-case time complexity is O(N); expected worst-case space complexity is O(N), beyond input storage (not counting the storage required for input arguments). Elements of input arrays can be modified.