Partitions

You are given a 1D integer array B containing A integers.

Count the number of ways to split all the elements of the array into 3 contiguous parts so that the sum of elements in each part is the same.

Such that : sum(B[1],..B[i]) = sum(B[i+1],...B[j]) = sum(B[j+1],...B[n])

1 <= A <= 10⁵

-10⁹ <= B[i] <= 10⁹

First argument is an integer A.

Second argument is an 1D integer array B of size A.

Return a single integer denoting the number of ways to split the array B into three parts with the same sum.

Input 1:

 A = 5
 B = [1, 2, 3, 0, 3]

Input 2:

 A = 4
 B = [0, 1, -1, 0]

Output 1:

 2

Output 2:

 1

Explanation 1:

 There are no 2 ways to make partitions -
 1. (1,2)+(3)+(0,3).
 2. (1,2)+(3,0)+(3).

Explanation 2:

 There is only 1 way to make partition -
 1. (0)+(-1,1)+(0).