Count the triplets

Easy

Given an array of distinct integers. The task is to count all the triplets such that sum of two elements equals the third element.

 

Example 1:

Input:
N = 4
arr[] = {1, 5, 3, 2}
Output: 2
Explanation: There are 2 triplets: 
1 + 2 = 3 and 3 +2 = 5 

​Example 2:

Input: 
N = 3
arr[] = {2, 3, 4}
Output: 0
Explanation: No such triplet exits

Your Task:  
You don't need to read input or print anything. Your task is to complete the function countTriplet() which takes the array arr[] and N as inputs and returns the triplet count

Expected Time Complexity: O(N²)
Expected Auxiliary Space: O(1)

Constraints:
1 ≤ N ≤ 10³
1 ≤ arr[i] ≤ 10⁵