<p>Given the <code>root</code> of a binary search tree and the lowest and highest boundaries as <code>low</code> and <code>high</code>, trim the tree so that all its elements lies in <code>[low, high]</code>. Trimming the tree should <strong>not</strong> 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 <strong>unique answer</strong>.</p> <p>Return <em>the root of the trimmed binary search tree</em>. Note that the root may change depending on the given bounds.</p> <p> </p> <p><strong>Example 1:</strong></p> <img alt="" src="https://assets.leetcode.com/uploads/2020/09/09/trim1.jpg" style="width: 450px; height: 126px;" /> <pre> <strong>Input:</strong> root = [1,0,2], low = 1, high = 2 <strong>Output:</strong> [1,null,2] </pre> <p><strong>Example 2:</strong></p> <img alt="" src="https://assets.leetcode.com/uploads/2020/09/09/trim2.jpg" style="width: 450px; height: 277px;" /> <pre> <strong>Input:</strong> root = [3,0,4,null,2,null,null,1], low = 1, high = 3 <strong>Output:</strong> [3,2,null,1] </pre> <p> </p> <p><strong>Constraints:</strong></p> <ul> <li>The number of nodes in the tree in the range <code>[1, 10<sup>4</sup>]</code>.</li> <li><code>0 <= Node.val <= 10<sup>4</sup></code></li> <li>The value of each node in the tree is <strong>unique</strong>.</li> <li><code>root</code> is guaranteed to be a valid binary search tree.</li> <li><code>0 <= low <= high <= 10<sup>4</sup></code></li> </ul>