Description
https://leetcode.com/problems/closest-binary-search-tree-value/
Given the root of a binary search tree and a target value, return the value in the BST that is closest to the target.
Example 1:
Input: root = [4,2,5,1,3], target = 3.714286 Output: 4
Example 2:
Input: root = [1], target = 4.428571 Output: 1
Constraints:
- The number of nodes in the tree is in the range
[1, 104]. 0 <= Node.val <= 109-109 <= target <= 109
Explanation
Base on the characteristics of binary search tree to search for the target.
Python Solution
# 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 closestValue(self, root: TreeNode, target: float) -> int:
self.closest = None
self.search(root, target)
return self.closest.val
def search(self, root, target):
if not root:
return
if not self.closest or abs(root.val - target) < abs(self.closest.val - target):
self.closest = root
if target < root.val:
self.search(root.left, target)
elif target > root.val:
self.search(root.right, target)
- Time Complexity: O(log(N)).
- Space Complexity: O(1).