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[10/9] 653. Two Sum IV - Input is a BST
본문
Easy
5063223Add to ListShareGiven 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:
Input: root = [5,3,6,2,4,null,7], k = 9 Output: true
Example 2:
Input: root = [5,3,6,2,4,null,7], k = 28 Output: false
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
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# Definition for a binary tree node.
# class TreeNode:
# def __init__(self, val=0, left=None, right=None):
# self.val = val
# self.left = left
# self.right = right
class Solution:
def findTarget(self, root: Optional[TreeNode], k: int) -> bool:
lookingfor = set()
def dfs(node):
if not node: return False
if node.val in lookingfor:
return True
lookingfor.add(k-node.val)
return dfs(node.left) or dfs(node.right)
return dfs(root)