Sum Binary-Search-Tree Values inside an Inclusive Interval
Company: Google
Role: Software Engineer
Category: Coding & Algorithms
Difficulty: easy
Interview Round: Other
### Problem
Given a binary-search-tree root and bounds low and high, return the sum of every node value in the inclusive interval `[low,high]`.
```cpp
class Solution {
public:
int rangeSumBST(TreeNode* root, int low, int high);
};
```
### Examples
**Example 1:**
```text
Input: root = [8,3,10,1,6,null,14], low = 3, high = 10
Output: 27
Explanation: Included values are3,6,8,and10, totaling27.
```
**Example 2:**
```text
Input: root = [5], low = 6, high = 9
Output: 0
Explanation: The only node is outside the interval.
```
### Constraints
- The tree has1 to `2*10^4` nodes.
- `1 <= Node.val <= 10^5`; node values are unique.
- `1 <= low <= high <= 10^5`.
### Contract considerations
The caller supplies the original TreeNode structure. Example arrays only display the tree; the API is not converted to an array function.
```hint Read the boundary condition
BST ordering can rule out a whole subtree once its parent falls beyond a range boundary.
```
### Boundary reminders
The caller supplies the original TreeNode structure. Example arrays only display the tree; the API is not converted to an array function.
Overview: Sum Binary-Search-Tree Values inside an Inclusive Interval. Given a binary-search-tree root and bounds low and high, return the sum of every node value in the inclusive interval [low,high].