判断某数组是不是二叉树的后序遍历序列 python递归与非递归解法

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python 递归

class Solution:
    def VerifySquenceOfBST(self, sequence):
        # write code here
        if len(sequence) <= 0 or sequence == None:
            return False
        length = len(sequence)
        root = sequence[-1]
        i, j = 0, 0

        # i 的范围是[0, length - 1]
        for i in range(length):
            if sequence[i] > root:
                break

        # j的范围是[i, length - 1]
        for j in range(i, length):
            if sequence[j] < root:
                return False

        left = True
        if i > 0:
            left = self.VerifySquenceOfBST(sequence[:i])

        right = True
        if j < length - 1:
            right = self.VerifySquenceOfBST(sequence[i:-1])

        return left and right

python 非递归

class Solution1:
    def VerifySquenceOfBST(self, sequence):
        # write code here
        if len(sequence) == 0:
            return False
        length = len(sequence) - 1
        i = 0
        while length != 0:
            while sequence[i] < sequence[length]:
                i += 1
            while sequence[i] > sequence[length]:
                i += 1
            if i < length:
                return False
            length -= 1
            i = 0
        return True