二叉搜索树的后续遍历

# -*- coding:utf-8 -*-
class Solution:
    def VerifySquenceOfBST(self, sequence):
        # write code here
        if not sequence:
            return False
        root = sequence[-1]
        i = 0
        while sequence[i] < root:
            i = i+ 1
        for j in range(i,len(sequence)-1):
            if sequence[j] < root:
                return False
        left = sequence[:i]
        right =sequence[i:len(sequence)-1]
        leftIs = True
        rightIs =True
        if len(left) > 0:
            leftIs = self.VerifySquenceOfBST(left)
        if len(right) > 0:
            rightIs = self.VerifySquenceOfBST(right)
        return leftIs and rightIs