Update 0654.最大二叉树，添加C#版

problems/0654.最大二叉树.md

@@ -582,6 +582,21 @@ impl Solution {
     }
 }
 ```
+### C#
+```C#
+public TreeNode ConstructMaximumBinaryTree(int[] nums)
+{
+    if (nums.Length == 0) return null;
+    int rootValue = nums.Max();
+    TreeNode root = new TreeNode(rootValue);
+    int rootIndex = Array.IndexOf(nums, rootValue);
+
+    root.left = ConstructMaximumBinaryTree(nums.Take(rootIndex).ToArray());
+    root.right = ConstructMaximumBinaryTree(nums.Skip(rootIndex + 1).ToArray());
+    return root;
+
+}
+```
 
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