Accenture OA-28 2024

Problem Description

Let j and k be two indices in an array A.
If j < k and A[j] > A[k], then the pair (j,k) is known as an "Inversion pair".
You are required to implement the following function:
int InversionCount(int *A, int n);
The function accepts an array 'A' of 'n' unique integers as its argument. You are required to calculate the number of 'Inversion pair' in an array A, and return.

Note:
If 'A' is NULL (None in case of python), return -1
If 'n' < 2, return 0

Input Format:

• The input consists of an array A of n integers.

Output Format:

Output the total number of inversion pairs in the array.

Constraints:

• 0 ≤ n ≤ 10^5
• -10^9 ≤ A[i] ≤ 10^9

Example

Sample Input:

[2, 3, 1, 5, 4]

Sample Output:

3

Explanation:
The inversion pairs are:

1. (1, 2)
2. (1, 3)
3. (4, 5)