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145.py
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'''
Given a binary tree, return the postorder traversal of its nodes' values.
Example:
Input: [1,null,2,3]
1
\
2
/
3
Output: [3,2,1]
Follow up: Recursive solution is trivial, could you do it iteratively?
'''
# Definition for a binary tree node.
# class TreeNode(object):
# def __init__(self, x):
# self.val = x
# self.left = None
# self.right = None
classSolution(object):
defpostorderTraversal(self, root):
"""
:type root: TreeNode
:rtype: List[int]
"""
result= []
defrecursive(root, result):
ifnotroot:
return
recursive(root.left, result)
recursive(root.right, result)
result.append(root.val)
recursive(root, result)
returnresult
# Definition for a binary tree node.
# class TreeNode(object):
# def __init__(self, x):
# self.val = x
# self.left = None
# self.right = None
classSolution(object):
defpostorderTraversal(self, root):
"""
:type root: TreeNode
:rtype: List[int]
"""
ifnotroot:
return []
stack, result= [], []
whileTrue:
whileroot:
ifroot.right:
stack.append(root.right)
stack.append(root)
root=root.left
root=stack.pop()
ifroot.rightandstackandstack[-1] ==root.right:
stack.pop()
stack.append(root)
root=root.right
else:
result.append(root.val)
root=None
iflen(stack)<=0:
break
returnresult
