python 實現二叉樹並求其高度

二叉樹的實現：建立節點類

class

treenode
:def
__init__
(self, x)
:        self.left =
none
self.right =
none
self.val = x

class

solution
:#從上往下列印出二叉樹的每個節點，同層節點從左至右列印
defprintfromtoptobottom
(self, root)
:        array =
result =
if root ==
none
:return result
while array:
newnode = array.pop(0)
if newnode.left !=
none
:if newnode.right !=
none
:return result
# 給定二叉樹的前序遍歷和中序遍歷，獲得該二叉樹
defgetbstwithpretin
(self, pre, tin):if
len(pre)==0
|len
(tin)==0
:return
none
root = treenode(pre[0]
)for order,item in
enumerate
(tin)
:if root .val == item:
root.left = self.getbstwithpretin(pre[
1:order+1]
, tin[
:order]
)                root.right = self.getbstwithpretin(pre[order+1:
], tin[order+1:
])return root
#求二叉樹的最大深度（即高度）
defmaxdepth
(self, root)
:"""
:type root: treenode
:rtype: int
"""ifnot root:
# 遞迴邊界
return
0else
:            l =
1+ self.maxdepth(root.left)
# 遞迴
r =1+ self.maxdepth(root.right)
return
max(l, r)

if __name__ ==

'__main__'
:    solution = solution(
)#preorder_seq = [1, 2, 4, 7, 3, 5, 6, 8]
# middleorder_seq = [4, 7, 2, 1, 5, 3, 8, 6]
preorder_seq=
["a"
,"b"
,"c"
,"d"
,"e"
,"f"
,"g"
]    middleorder_seq=
["g"
,"f"
,"e"
,"d"
,"c"
,"b"
,"a"
]    treeroot1 = solution.getbstwithpretin(preorder_seq, middleorder_seq)if1
:        newarray = solution.printfromtoptobottom(treeroot1)
print
(newarray)
print
(solution.maxdepth(treeroot1)
)

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