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Update 0226.翻转二叉树.md
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@ -314,81 +314,158 @@ class Solution {
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递归法:前序遍历:
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递归法:前序遍历:
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```python
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```python
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# Definition for a binary tree node.
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# class TreeNode:
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# def __init__(self, val=0, left=None, right=None):
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# self.val = val
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# self.left = left
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# self.right = right
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class Solution:
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class Solution:
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def invertTree(self, root: TreeNode) -> TreeNode:
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def invertTree(self, root: TreeNode) -> TreeNode:
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if not root:
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if not root:
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return None
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return None
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root.left, root.right = root.right, root.left #中
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root.left, root.right = root.right, root.left
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self.invertTree(root.left) #左
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self.invertTree(root.left)
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self.invertTree(root.right) #右
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self.invertTree(root.right)
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return root
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return root
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```
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```
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递归法:后序遍历:
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迭代法:前序遍历:
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```python
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```python
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# Definition for a binary tree node.
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# class TreeNode:
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# def __init__(self, val=0, left=None, right=None):
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# self.val = val
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# self.left = left
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# self.right = right
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class Solution:
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class Solution:
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def invertTree(self, root: TreeNode) -> TreeNode:
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def invertTree(self, root: TreeNode) -> TreeNode:
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if root is None:
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if not root:
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return None
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stack = [root]
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while stack:
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node = stack.pop()
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node.left, node.right = node.right, node.left
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if node.left:
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stack.append(node.left)
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if node.right:
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stack.append(node.right)
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return root
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```
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递归法:中序遍历:
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```python
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# Definition for a binary tree node.
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# class TreeNode:
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# def __init__(self, val=0, left=None, right=None):
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# self.val = val
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# self.left = left
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# self.right = right
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class Solution:
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def invertTree(self, root: TreeNode) -> TreeNode:
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if not root:
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return None
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self.invertTree(root.left)
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root.left, root.right = root.right, root.left
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self.invertTree(root.left)
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return root
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```
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迭代法:中序遍历:
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```python
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# Definition for a binary tree node.
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# class TreeNode:
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# def __init__(self, val=0, left=None, right=None):
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# self.val = val
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# self.left = left
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# self.right = right
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class Solution:
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def invertTree(self, root: TreeNode) -> TreeNode:
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if not root:
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return None
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stack = [root]
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while stack:
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node = stack.pop()
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if node.left:
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stack.append(node.left)
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node.left, node.right = node.right, node.left
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if node.left:
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stack.append(node.left)
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return root
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```
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递归法:后序遍历:
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```python
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# Definition for a binary tree node.
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# class TreeNode:
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# def __init__(self, val=0, left=None, right=None):
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# self.val = val
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# self.left = left
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# self.right = right
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class Solution:
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def invertTree(self, root: TreeNode) -> TreeNode:
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if not root:
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return None
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return None
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self.invertTree(root.left)
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self.invertTree(root.left)
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self.invertTree(root.right)
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self.invertTree(root.right)
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root.left, root.right = root.right, root.left
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root.left, root.right = root.right, root.left
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return root
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return root
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```
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```
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迭代法:深度优先遍历(前序遍历):
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迭代法:后序遍历:
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```python
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```python
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# Definition for a binary tree node.
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# class TreeNode:
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# def __init__(self, val=0, left=None, right=None):
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# self.val = val
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# self.left = left
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# self.right = right
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class Solution:
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class Solution:
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def invertTree(self, root: TreeNode) -> TreeNode:
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def invertTree(self, root: TreeNode) -> TreeNode:
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if not root:
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if not root:
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return root
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return None
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st = []
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stack = [root]
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st.append(root)
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while stack:
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while st:
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node = stack.pop()
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node = st.pop()
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node.left, node.right = node.right, node.left #中
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if node.right:
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st.append(node.right) #右
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if node.left:
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if node.left:
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st.append(node.left) #左
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stack.append(node.left)
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if node.right:
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stack.append(node.right)
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node.left, node.right = node.right, node.left
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return root
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return root
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```
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```
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迭代法:广度优先遍历(层序遍历):
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迭代法:广度优先遍历(层序遍历):
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```python
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```python
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import collections
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# Definition for a binary tree node.
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# class TreeNode:
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# def __init__(self, val=0, left=None, right=None):
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# self.val = val
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# self.left = left
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# self.right = right
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class Solution:
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class Solution:
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def invertTree(self, root: TreeNode) -> TreeNode:
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def invertTree(self, root: TreeNode) -> TreeNode:
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queue = collections.deque() #使用deque()
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if not root:
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if root:
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return None
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queue.append(root)
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queue = collections.deque([root])
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while queue:
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while queue:
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size = len(queue)
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for i in range(len(queue)):
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for i in range(size):
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node = queue.popleft()
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node = queue.popleft()
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node.left, node.right = node.right, node.left #节点处理
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node.left, node.right = node.right, node.left
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if node.left:
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if node.left: queue.append(node.left)
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queue.append(node.left)
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if node.right: queue.append(node.right)
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if node.right:
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queue.append(node.right)
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return root
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```
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迭代法:广度优先遍历(层序遍历),和之前的层序遍历写法一致:
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```python
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class Solution:
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def invertTree(self, root: Optional[TreeNode]) -> Optional[TreeNode]:
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if not root: return root
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from collections import deque
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que=deque([root])
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while que:
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size=len(que)
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for i in range(size):
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cur=que.popleft()
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cur.left, cur.right = cur.right, cur.left
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if cur.left: que.append(cur.left)
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if cur.right: que.append(cur.right)
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return root
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return root
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```
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```
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### Go
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### Go
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递归版本的前序遍历
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递归版本的前序遍历
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