Description
https://leetcode.com/problems/range-sum-of-bst/solution/
Given the root node of a binary search tree, return the sum of values of all nodes with a value in the range [low, high].
Example 1:
Input: root = [10,5,15,3,7,null,18], low = 7, high = 15 Output: 32
Example 2:
Input: root = [10,5,15,3,7,13,18,1,null,6], low = 6, high = 10 Output: 23
Constraints:
- The number of nodes in the tree is in the range
[1, 2 * 104]. 1 <= Node.val <= 1051 <= low <= high <= 105- All
Node.valare unique.
Explanation
Depth first search to add qualified numbers to the global sum.
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 rangeSumBST(self, root: TreeNode, low: int, high: int) -> int:
self.result = 0
self.helper(root, low, high)
return self.result
def helper(self, root, low, high):
if not root:
return
if root.val >= low and root.val <= high:
self.result += root.val
self.helper(root.left, low, high)
self.helper(root.right, low, high)
- Time Complexity: O(N)
- Space Complexity: O(N)