Sum of k smallest elements in BST
Easy Accuracy: 65.96% Submissions: 1334 Points: 2

 Given a Binary Search Tree. Find sum of all elements smaller than and equal to Kth smallest element.

Example 1:

Input: 
          20
        /    \
       8     22
     /    \
    4     12
         /    \
        10    14   , K=3

Output: 22
Explanation:
Sum of 3 smallest elements are: 
4 + 8 + 10 = 22
Example 2:
Input:
     10
    /  \
   5    11
  / \ 
 4   7
      \
       8 , K=2

Output: 9
Explanation:
The sum of two smallest elements 
is 4+5=9.
 
Your task:
You don't need to read input or print anything. Your task is to complete the function sum() which takes the root node and an integer K as input parameters and returns the sum of all elements smaller than and equal to kth smallest element.
 
Expected Time Complexity: O(K)
Expected Auxiliary Space: O(1)
 
Constraints:
1<=Number of nodes in BST<=100
1<=K<=N

  

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Sum of k smallest elements in BST

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