Subarray Sum Equals K

1 <= length of the array <= 50000
-1000 <= A[i] <= 1000

The first argument given is the integer array A.
The second argument given is integer B.

Return the total number of subarrays having sum equals to B.

Input 1:
A = [1, 0, 1]
B = 1

Input 2:
A = [0, 0, 0]
B = 0

Output 1:
4

Output 2:
6

Explanation 1:
[1], [1, 0], [0, 1] and [1] are four subarrays having sum 1.

Explanation 2:
All the possible subarrays having sum 0.