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Java-based LeetCode algorithm problem solutions, regularly updated
669\. Trim a Binary Search Tree
Medium
Given the `root` of a binary search tree and the lowest and highest boundaries as `low` and `high`, trim the tree so that all its elements lies in `[low, high]`. Trimming the tree should **not** change the relative structure of the elements that will remain in the tree (i.e., any node's descendant should remain a descendant). It can be proven that there is a **unique answer**.
Return _the root of the trimmed binary search tree_. Note that the root may change depending on the given bounds.
**Example 1:**
![](https://assets.leetcode.com/uploads/2020/09/09/trim1.jpg)
**Input:** root = [1,0,2], low = 1, high = 2
**Output:** [1,null,2]
**Example 2:**
![](https://assets.leetcode.com/uploads/2020/09/09/trim2.jpg)
**Input:** root = [3,0,4,null,2,null,null,1], low = 1, high = 3
**Output:** [3,2,null,1]
**Constraints:**
* The number of nodes in the tree in the range [1, 104]
.
* 0 <= Node.val <= 104
* The value of each node in the tree is **unique**.
* `root` is guaranteed to be a valid binary search tree.
* 0 <= low <= high <= 104