Convert Sorted List to Binary Search Tree

Question

• leetcode - Convert Sorted List to Binary Search Tree | LeetCode OJ
• lintcode - (106) 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.

• reference

# Definition for a  binary tree node
# class TreeNode:
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None
#
# Definition for singly-linked list.
# class ListNode:
#     def __init__(self, x):
#         self.val = x
#         self.next = None

class Solution:
    # @param head, a list node
    # @return a tree node
    def sortedArrayToBST(self, array):
        length = len(array)
        if length==0: return None
        if length==1: return TreeNode(array[0])
        root = TreeNode(array[length/2])
        root.left = self.sortedArrayToBST(array[:length/2])
        root.right = self.sortedArrayToBST(array[length/2+1:])
        return root

    def sortedListToBST(self, head):
        array = []
        p = head
        while p:
            array.append(p.val)
            p = p.next
        return self.sortedArrayToBST(array)