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.
Example 1:
Input:
2
/ \
1 3
sum = 5
Output: 1
Explanation:
Nodes with value 2 and 3 sum up to 5.
Example 2:
Input:
6
/
5
/
3
/ \
1 4
sum = 2
Output: 0
Explanation:
There's no pair that sums up to 2.
Your Task:
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).
Constraints:
1 ≤ Number of Nodes ≤ 10^{5}
1 ≤ Sum ≤ 10^{6}

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