Leetcode 108. Convert Sorted Array to Binary Search Tree

https://leetcode.com/problems/convert-sorted-array-to-binary-search-tree/

Because it requires the height balanced BST, just cut the list into half and half and go recursion.

Solution:

# T:O(n) S:O(lgn)
class Solution:
    # @param num, a list of integers
    # @return a tree node
    def sortedArrayToBST(self, num):
        length = len(num)
        if length == 0:
            return None
        if length == 1:
            return TreeNode(num[0])
        root = TreeNode(num[length / 2])
        root.left = self.sortedArrayToBST(num[:length/2])
        root.right = self.sortedArrayToBST(num[length/2 + 1:])
        return root

Run Time: 96 ms