Given a Binary Search Tree and a target sum. Check whether there's a pair of Nodes in the BST with value summing up to the target sum.
sum = 5
Nodes with value 2 and 3 sum up to 5.
sum = 2
There's no pair that sums up to 2.
You don't need to read input or print anything. Your task is to complete the function isPairPresent() that takes a root node and a target value as a parameter and returns 1 if there's a pair of Nodes in the BST with values summing up to the target sum, else returns 0.
Expected Time Complexity: O(N).
Expected Auxiliary Space: O(Height of the BST).
1 ≤ Number of Nodes ≤ 105
1 ≤ Sum ≤ 106