Given an array and integer m, check how many unique contiguous subsets exist in the array such that each subset has m odd numbers.

Ex1: [2,5,6,9] m=1

[2,5], [5,6], [2,5,6],[5],[6,9],[9] are the possible subsets with m=1 odd numbers.

Result: 6

Ex2: [2,5,6,9] m=2

[2,5,6,9] and [5,6,9]

Result:2

What is better than a O(n2) solution. Can it be done with backtracking(is it needed)?