0450.删除二叉搜索树中的节点 加入Ruby递归实现

problems/0450.删除二叉搜索树中的节点.md

@@ -801,6 +801,40 @@ impl Solution {
     }
 ```
 
+### Ruby
+> 递归法：
+```ruby
+# @param {TreeNode} root
+# @param {Integer} key
+# @return {TreeNode}
+def delete_node(root, key)
+    return nil if root.nil?
+
+    right = root.right
+    left = root.left
+
+    if root.val == key
+        return right if left.nil?
+        return left if right.nil?
+
+        node = right
+        while node.left
+            node = node.left
+        end
+        node.left = left
+
+        return right
+    end
+
+    if root.val > key
+        root.left = delete_node(left, key)
+    else
+        root.right = delete_node(right, key)
+    end
+
+    return root
+end
+```
 
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