Refactor MaxDepth method and add BuildTree method

Changed MaxDepth to a static method in MaximumDepthOfBinaryTree.cs for easier access.

Added BuildTree method in ConstructBinaryTreeFromPreorderAndInorderTraversal.cs to construct a binary tree from preorder and inorder arrays, including null checks and recursive subtree construction. Added necessary using directives.

Author: ewdlop

101-110/104.MaximumDepthOfBinaryTree.cs

@@ -4,7 +4,7 @@ namespace LeetCodeNote;
 
 public static partial class Solution
 {
-    public int MaxDepth(TreeNode root)
+    public static int MaxDepth(TreeNode root)
     {
         if (root == null) return 0;
 

101-110/105.ConstructBinaryTreeFromPreorderAndInorderTraversal.cs

@@ -0,0 +1,26 @@
+using System;
+using System.Linq;
+
+namespace LeetCodeNote;
+
+public static partial class Solution
+{
+    /// <summary>
+    /// need more details and understanding
+    /// </summary>
+    /// <param name="preorder"></param>
+    /// <param name="inorder"></param>
+    /// <returns></returns>
+    public static TreeNode BuildTree(int[] preorder, int[] inorder)
+    {
+        if (preorder is null || !preorder.Any() ||
+           inorder is null || !inorder.Any()) return null;
+
+        TreeNode root = new TreeNode(preorder[0]);
+        int middle = Array.IndexOf(inorder, preorder[0]);
+        root.left = BuildTree(preorder[1..(middle + 1)], inorder[..middle]);
+        root.right = BuildTree(preorder[(middle + 1)..], inorder[(middle + 1)..]);
+
+        return root;
+    }
+}