Find a pair with given target in BST
Medium Accuracy: 47.17% Submissions: 30068 Points: 4

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 ≤ 105
1 ≤ Sum ≤ 106

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Find a pair with given target in BST

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