Delete Node in a BST
<p>Given a root node reference of a BST and a key, delete the node with the given key in the BST. Return <em>the <strong>root node reference</strong> (possibly updated) of the BST</em>.</p>

<p>Basically, the deletion can be divided into two stages:</p>

<ol>
	<li>Search for a node to remove.</li>
	<li>If the node is found, delete the node.</li>
</ol>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>
<img alt="" src="https://fastly.jsdelivr.net/gh/doocs/leetcode@main/solution/0400-0499/0450.Delete%20Node%20in%20a%20BST/images/del_node_1.jpg" style="width: 800px; height: 214px;" />
<pre>
<strong>Input:</strong> root = [5,3,6,2,4,null,7], key = 3
<strong>Output:</strong> [5,4,6,2,null,null,7]
<strong>Explanation:</strong> Given key to delete is 3. So we find the node with value 3 and delete it.
One valid answer is [5,4,6,2,null,null,7], shown in the above BST.
Please notice that another valid answer is [5,2,6,null,4,null,7] and it&#39;s also accepted.
<img alt="" src="https://fastly.jsdelivr.net/gh/doocs/leetcode@main/solution/0400-0499/0450.Delete%20Node%20in%20a%20BST/images/del_node_supp.jpg" style="width: 350px; height: 255px;" />
</pre>

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> root = [5,3,6,2,4,null,7], key = 0
<strong>Output:</strong> [5,3,6,2,4,null,7]
<strong>Explanation:</strong> The tree does not contain a node with value = 0.
</pre>

<p><strong class="example">Example 3:</strong></p>

<pre>
<strong>Input:</strong> root = [], key = 0
<strong>Output:</strong> []
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li>The number of nodes in the tree is in the range <code>[0, 10<sup>4</sup>]</code>.</li>
	<li><code>-10<sup>5</sup> &lt;= Node.val &lt;= 10<sup>5</sup></code></li>
	<li>Each node has a <strong>unique</strong> value.</li>
	<li><code>root</code> is a valid binary search tree.</li>
	<li><code>-10<sup>5</sup> &lt;= key &lt;= 10<sup>5</sup></code></li>
</ul>

<p>&nbsp;</p>
<p><strong>Follow up:</strong> Could you solve it with time complexity <code>O(height of tree)</code>?</p>
Tree; Binary Search Tree; Binary Tree
/**
 * Definition for a binary tree node.
 * class TreeNode {
 *     val: number
 *     left: TreeNode | null
 *     right: TreeNode | null
 *     constructor(val?: number, left?: TreeNode | null, right?: TreeNode | null) {
 *         this.val = (val===undefined ? 0 : val)
 *         this.left = (left===undefined ? null : left)
 *         this.right = (right===undefined ? null : right)
 *     }
 * }
 */

function deleteNode(root: TreeNode | null, key: number): TreeNode | null {
    if (root == null) {
        return root;
    }
    const { val, left, right } = root;
    if (val > key) {
        root.left = deleteNode(left, key);
    } else if (val < key) {
        root.right = deleteNode(right, key);
    } else {
        if (left == null && right == null) {
            root = null;
        } else if (left == null || right == null) {
            root = left || right;
        } else {
            if (right.left == null) {
                right.left = left;
                root = right;
            } else {
                let minPreNode = right;
                while (minPreNode.left.left != null) {
                    minPreNode = minPreNode.left;
                }
                const minVal = minPreNode.left.val;
                root.val = minVal;
                minPreNode.left = deleteNode(minPreNode.left, minVal);
            }
        }
    }
    return root;
}
