Update 0450.删除二叉搜索树中的节点.md

0450.删除二叉搜索树中的节点.md 添加python3迭代法

problems/0450.删除二叉搜索树中的节点.md

@@ -344,6 +344,48 @@ class Solution:
         return root
 ```
 
+**迭代法**
+```python
+class Solution:
+    def deleteNode(self, root: Optional[TreeNode], key: int) -> Optional[TreeNode]:
+        # 找到节点后分两步，1. 把节点的左子树和右子树连起来，2. 把右子树跟父节点连起来
+        # root is None
+        if not root: return root
+        p = root
+        last = None
+        while p:
+            if p.val==key:
+                # 1. connect left to right
+                # right is not None -> left is None | left is not None
+                if p.right:
+                    if p.left:
+                        node = p.right
+                        while node.left:
+                            node = node.left
+                        node.left = p.left
+                    right = p.right
+                else:
+                # right is None -> right=left
+                    right = p.left
+                # 2. connect right to last
+                if last==None:
+                    root = right
+                elif last.val>key:
+                    last.left = right
+                else:
+                    last.right = right
+                # 3. return
+                break
+            else:
+                # Update last and continue
+                last = p
+                if p.val>key:
+                    p = p.left
+                else:
+                    p = p.right
+        return root
+```
+
 ## Go
 ```Go
 // 递归版本