diff --git a/problems/0538.把二叉搜索树转换为累加树.md b/problems/0538.把二叉搜索树转换为累加树.md index ad5310e1..ad4decc5 100644 --- a/problems/0538.把二叉搜索树转换为累加树.md +++ b/problems/0538.把二叉搜索树转换为累加树.md @@ -200,8 +200,30 @@ class Solution { ``` ## Python -**递归** - +递归法(版本一) +```python +# Definition for a binary tree node. +# class TreeNode: +# def __init__(self, val=0, left=None, right=None): +# self.val = val +# self.left = left +# self.right = right +class Solution: + def convertBST(self, root: TreeNode) -> TreeNode: + self.pre = 0 # 记录前一个节点的数值 + self.traversal(root) + return root + def traversal(self, cur): + if cur is None: + return + self.traversal(cur.right) + cur.val += self.pre + self.pre = cur.val + self.traversal(cur.left) + + +``` +递归法(版本二) ```python # Definition for a binary tree node. # class TreeNode: @@ -234,7 +256,32 @@ class Solution: return root ``` -**迭代** +迭代法(版本一) +```python +class Solution: + def __init__(self): + self.pre = 0 # 记录前一个节点的数值 + + def traversal(self, root): + stack = [] + cur = root + while cur or stack: + if cur: + stack.append(cur) + cur = cur.right # 右 + else: + cur = stack.pop() # 中 + cur.val += self.pre + self.pre = cur.val + cur = cur.left # 左 + + def convertBST(self, root): + self.pre = 0 + self.traversal(root) + return root + +``` +迭代法(版本二) ```python class Solution: def convertBST(self, root: Optional[TreeNode]) -> Optional[TreeNode]: