C# Simple recursion DFS
Runtime: 240 ms, faster than 85.66% of C# online submissions for Binary Tree Level Order Traversal.\nMemory Usage: 30.8 MB, less than 20.00% of C# online submis
Runtime: 240 ms, faster than 85.66% of C# online submissions for Binary Tree Level Order Traversal.\nMemory Usage: 30.8 MB, less than 20.00% of C# online submissions for Binary Tree Level Order Traversal.\n\n```\n    public IList<IList<int>> LevelOrder(TreeNode root)\n    {\n        var result = new List<IList<int>>();\n        \n        if (root == null) return result;\n        \n        result.Add(new List<int>() { root.val });\n        \n        TraverseTree(root.left, result);\n        TraverseTree(root.right, result);\n        \n        return result;\n    }\n    \n    private void TraverseTree(TreeNode node, IList<IList<int>> result, int depth = 0)\n    {\n        if (node == null) return;\n        if (result.Count == ++depth) result.Add(new List<int>());\n        \n        result[depth].Add(node.val);\n        \n        TraverseTree(node.left, result, depth);\n        TraverseTree(node.right, result, depth);\n    }\n```
['Depth-First Search', 'Interactive']