Update 0513.找树左下方的值，添加C#递归版

problems/0513.找树左下角的值.md

@@ -684,6 +684,38 @@ impl Solution {
     }
 }
 ```
+### C#
+```C#
+//递归
+int maxDepth = -1;
+int res = 0;
+public int FindBottomLeftValue(TreeNode root)
+{
+    Traversal(root, 0);
+    return res;
+}
+public void Traversal(TreeNode root, int depth)
+{
+    if (root.left == null && root.right == null)
+    {
+        if (depth > maxDepth)
+        {
+            maxDepth = depth;
+            res = root.val;
+        }
+        return;
+    }
+    if (root.left != null)
+    {
+        Traversal(root.left, depth + 1);
+    }
+    if (root.right != null)
+    {
+        Traversal(root.right, depth + 1);
+    }
+    return;
+}
+```
 
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