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更新 144.二叉树的前序遍历 python3版本

更新 145.二叉树的后序遍历 python3版本更新 94.二叉树的中序遍历 python3版本

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problems
- 二叉树的迭代遍历.md

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`‎problems/二叉树的迭代遍历.md‎`

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`@@ -160,6 +160,68 @@ Java:`
`160`	`160`
`161`	`161`
`162`	`162`	`Python:`
	`163`	+```python3
	`164`	`+# 前序遍历-迭代-LC144_二叉树的前序遍历`
	`165`	`+class Solution:`
	`166`	`+ def preorderTraversal(self, root: TreeNode) -> List[int]:`
	`167`	`+ # 根结点为空则返回空列表`
	`168`	`+ if not root:`
	`169`	`+ return []`
	`170`	`+ stack = [root]`
	`171`	`+ result = []`
	`172`	`+ while stack:`
	`173`	`+ node = stack.pop()`
	`174`	`+ # 中结点先处理`
	`175`	`+ result.append(node.val)`
	`176`	`+ # 右孩子先入栈`
	`177`	`+ if node.right:`
	`178`	`+ stack.append(node.right)`
	`179`	`+ # 左孩子后入栈`
	`180`	`+ if node.left:`
	`181`	`+ stack.append(node.left)`
	`182`	`+ return result`
	`183`	`+`
	`184`	`+# 中序遍历-迭代-LC94_二叉树的中序遍历`
	`185`	`+class Solution:`
	`186`	`+ def inorderTraversal(self, root: TreeNode) -> List[int]:`
	`187`	`+ if not root:`
	`188`	`+ return []`
	`189`	`+ stack = [] # 不能提前将root结点加入stack中`
	`190`	`+ result = []`
	`191`	`+ cur = root`
	`192`	`+ while cur or stack:`
	`193`	`+ # 先迭代访问最底层的左子树结点`
	`194`	`+ if cur:`
	`195`	`+ stack.append(cur)`
	`196`	`+ cur = cur.left`
	`197`	`+ # 到达最左结点后处理栈顶结点`
	`198`	`+ else:`
	`199`	`+ cur = stack.pop()`
	`200`	`+ result.append(cur.val)`
	`201`	`+ # 取栈顶元素右结点`
	`202`	`+ cur = cur.right`
	`203`	`+ return result`
	`204`	`+`
	`205`	`+# 后序遍历-迭代-LC145_二叉树的后序遍历`
	`206`	`+class Solution:`
	`207`	`+ def postorderTraversal(self, root: TreeNode) -> List[int]:`
	`208`	`+ if not root:`
	`209`	`+ return []`
	`210`	`+ stack = [root]`
	`211`	`+ result = []`
	`212`	`+ while stack:`
	`213`	`+ node = stack.pop()`
	`214`	`+ # 中结点先处理`
	`215`	`+ result.append(node.val)`
	`216`	`+ # 左孩子先入栈`
	`217`	`+ if node.left:`
	`218`	`+ stack.append(node.left)`
	`219`	`+ # 右孩子后入栈`
	`220`	`+ if node.right:`
	`221`	`+ stack.append(node.right)`
	`222`	`+ # 将最终的数组翻转`
	`223`	`+ return result[::-1]`
	`224`	+```
`163`	`225`
`164`	`226`
`165`	`227`	`Go:`

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