LeetCode — Two Sum IV Input is a BST

Given the root of a Binary Search Tree and a target number k, return true if there exist two elements in the BST such that their sum is equal to the given target.

Example 1:

Example 2:

Example 3:

Example 4:

Example 5:

Constraints:

  • The number of nodes in the tree is in the range [1, 104].
  • -104 <= Node.val <= 104
  • root is guaranteed to be a valid binary search tree.
  • -105 <= k <= 105

Solution:

Time complexity: O(N), where N represents the number of nodes in BST.

Space complexity: O(N)