Create SECURITY.md

# To get started with Dependabot version updates, you'll need to specify which
# package ecosystems to update and where the package manifests are located.
# Please see the documentation for all configuration options:
# https://docs.github.com/code-security/dependabot/dependabot-version-updates/configuration-options-for-the-dependabot.yml-file

version: 2
updates:
  - package-ecosystem: "" # See documentation for possible values
    directory: "/" # Location of package manifests
    schedule:
      interval: "weekly"

Create dependabot.yml

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <TargetFramework>net9.0</TargetFramework>
    <Nullable>enable</Nullable>

    <IsPackable>false</IsPackable>
  </PropertyGroup>

  <ItemGroup>
    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="16.11.0" />
    <PackageReference Include="xunit" Version="2.4.1" />
    <PackageReference Include="xunit.runner.visualstudio" Version="2.4.3">
      <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
      <PrivateAssets>all</PrivateAssets>
    </PackageReference>
    <PackageReference Include="coverlet.collector" Version="3.1.0">
      <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
      <PrivateAssets>all</PrivateAssets>
    </PackageReference>
  </ItemGroup>

  <ItemGroup>
    <ProjectReference Include="..\LeetCodeNote.csproj" />
  </ItemGroup>

</Project>

Update LeetCodeNote.Test.csproj

Introduces a new `Solution` class in the `LeetCodeNote` namespace with two static methods: `IsSymmetric` and `IsMirror`. The `IsSymmetric` method determines if a binary tree is symmetric by utilizing the `IsMirror` method, which recursively compares nodes for equality and checks their left and right subtrees. This implementation provides a structured approach to solving the symmetric tree problem.

Implement a new static partial class `Solution` with a `LevelOrder` method that performs level order traversal of a binary tree. The method returns a list of lists containing node values at each level, utilizing a queue for traversal and handling null nodes effectively.

Implemented the `IsSymmetric` and `IsMirror` methods in `101.SymmetricTree.cs` to check for symmetry in binary trees. Removed unnecessary using directive in `102.BinaryTreeLevelOrderTraversal.cs`. Introduced `103.BinaryTreeZigzagLevelOrderTraversal.cs` with a new `ZigzagLevelOrder` method for zigzag level order traversal of binary trees.

This commit introduces a new method `MaxDepth` in the `Solution` class under the `LeetCodeNote` namespace. The method computes the maximum depth of a binary tree using recursion, handling null input by returning 0. It evaluates the depths of the left and right subtrees and returns the greater value plus one.

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.