import gen
import alg

n = gen.nums
root = alg.constructMaximumBinaryTree(n)
# 前序遍历二叉树
def preorderTraversal(root):
    res = []
    def helper(root):
        # 如果树为空，则返回None
        if not root:
            return None
        res.append(root.val)
        helper(root.left)
        helper(root.right)
    helper(root)
    return res
# 输出遍历结果
print(preorderTraversal(root))