剑指offer 面试33题

# -*- coding:utf-8 -*-
class Solution:
    def VerifySquenceOfBST(self, sequence):
        # write code here
        if not sequence or len(sequence)<=0:
            return False
        root=sequence[-1]
        i=0
        
        #找出左小右大的分界点i,此时i属于右子树
        for node in sequence[:-1]:
            if node > root:
                break
            i+=1
        
        #如果在右子树中有比根节点小的值，直接返回False
        for node in sequence[i:-1]:
            if node < root:
                return False
        #判断左子树是否为二叉搜索树
        left=True
        if i>0:
            left=self.VerifySquenceOfBST(sequence[:i])
        #判断右子树是否为二叉搜索树
        right=True
        if i<len(sequence)-1:
            right=self.VerifySquenceOfBST(sequence[i+1:])
        return left and right