sortedArrayToBTS

這道題是說怎麼將一個升序的list轉換爲高度平衡二叉樹的節點

dayadayup:

1,反正記住二叉樹的題都用遞歸就對了

2，就是在用遞歸時一定要拼命找初始條件，初始結果

class Solution(object):
    def sortedArrayToBST(self, nums):
        """
        :type nums: List[int]
        :rtype: TreeNode
        """
        length = len(nums)
        if not length:
            return None
        if length == 1:
            root  = TreeNode(nums[0])
            return root
        index = length//2
        root = TreeNode(nums[index])
        root.left = self.sortedArrayToBST(nums[0:index])
        root.right = self.sortedArrayToBST(nums[index + 1:])
        return root