NameError : variable not defined

Question

对于简单的混淆，我们深表歉意。变量 'head' 已在使用全局引用的方法中被提及。但事实并非如此！

这是我的代码：

class Solution:
    head = None
    current = None
    def constructMaximumBinaryTree(self, nums: List[int]) -> 
TreeNode:
        m = nums.index(max(nums))
        global head
        global current
        if not head:
            head = TreeNode()
            head.val = max(nums)
            head.left = constructMaximumBinaryTree(self, nums[:m])
            head.right = constructMaximumBinaryTree(self, nums[m + 1:])
        elif not current:
            current = head
        else:
            pass
        current.left = constructMaximumBinaryTree(self, nums[:m])
        current.right = constructMaximumBinaryTree(self, nums[m+1:])
        return head

Answer 1

使用__init__魔术方法，并声明那些~~class~~实例变量，self（实例）是它的对象分配给 (self 实际上是 class):

class Solution:
    def __init__(self):
        self.head = None
        self.current = None
    def constructMaximumBinaryTree(self, nums: List[int]) -> TreeNode:
        m = nums.index(max(nums))
        if not self.head:
            self.head = TreeNode()
            self.head.val = max(nums)
            self.head.left = constructMaximumBinaryTree(self, nums[:m])
            self.head.right = constructMaximumBinaryTree(self, nums[m + 1:])
        elif not current:
            current = self.head
        else:
            pass
        current.left = constructMaximumBinaryTree(self, nums[:m])
        current.right = constructMaximumBinaryTree(self, nums[m+1:])
        return self.head

NameError : variable not defined

NameError : variable not defined

python

nameerror