创建一个接受平面数组并转换为树数据结构的递归函数

class TreeNode:
    def __init__(self, val=0, left=None, right=None):
        self.val = val
        self.left = left
        self.right = right

def array_to_tree(nums):
    if not nums:
        return None

    # 递归函数，将平面数组转换为树
    def build_tree(left, right):
        if left > right:
            return None

        mid = (left + right) // 2
        node = TreeNode(nums[mid])
        node.left = build_tree(left, mid - 1)
        node.right = build_tree(mid + 1, right)
        return node

    return build_tree(0, len(nums) - 1)