題目描述

輸入一個整數陣列，判斷該陣列是不是某二叉搜尋樹的後序遍歷的結果。如果是則輸出Yes,否則輸出No。假設輸入的陣列的任意兩個數字都互不相同。

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