【LEETCODE】109-Convert Sorted List to Binary Search Tree

Given a singly linked list where elements are sorted in ascending order, convert it to a height balanced BST.

# Definition for singly-linked list.
# class ListNode(object):
#     def __init__(self, x):
#         self.val = x
#         self.next = None

# Definition for a binary tree node.
# class TreeNode(object):
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None

class Solution(object):

def sortedarrayToBST(self,array):
length=len(array)
if length==0:
return None
if length==1:
return TreeNode(array[0])
root=TreeNode(array[int(length/2)])
root.left=self.sortedarrayToBST(array[:int(length/2)])
root.right=self.sortedarrayToBST(array[int(length/2)+1:])
return root

def sortedListToBST(self, head):
"""
:type head: ListNode
:rtype: TreeNode
"""
array=[]
p=head
while p:
array.append(p.val)                #把linkedlist转换成array，然后可以取值建tree
p=p.next
return self.sortedarrayToBST(array)