定义单链表的节点类和单链表类（参考附件），对如下的 PA(x)和PB(x)两个多项式求和，求和代码参考如下附图 。 PA(x)=3x11+7x8+4x3+5 ， PB(x)=8x117x8+10x6

好的，根据您的要求，我为您提供一个Python实现的单链表节点类和单链表类，并实现PA(x)和PB(x)两个多项式的求和。代码如下：

class ListNode:
    def __init__(self, val=0, next=None):
        self.val = val
        self.next = next

class LinkedList:
    def __init__(self):
        self.head = ListNode()

    def add(self, val):
        cur = self.head
        while cur.next is not None:
            cur = cur.next
        cur.next = ListNode(val)

    def __str__(self):
        cur = self.head.next
        s = ''
        while cur is not None:
            s += str(cur.val) + ' -> '
            cur = cur.next
        return s + 'None'

def add_poly(poly1, poly2):
    res = LinkedList()
    cur1, cur2 = poly1.head.next, poly2.head.next
    while cur1 and cur2:
        if cur1.val[1] == cur2.val[1]:
            res.add((cur1.val[0] + cur2.val[0], cur1.val[1]))
            cur1, cur2 = cur1.next, cur2.next
        elif cur1.val[1] > cur2.val[1]:
            res.add(cur1.val)
            cur1 = cur1.next
        else:
            res.add(cur2.val)
            cur2 = cur2.next
    while cur1:
        res.add(cur1.val)
        cur1 = cur1.next
    while cur2:
        res.add(cur2.val)
        cur2 = cur2.next
    return res

# 测试代码
pa = LinkedList()
pa.add((3, 11))
pa.add((7, 8))
pa.add((4, 3))
pa.add((5, 0))
print('PA(x):', pa)
pb = LinkedList()
pb.add((8, 11))
pb.add((7, 8))
pb.add((10, 6))
print('PB(x):', pb)
pc = add_poly(pa, pb)
print('PC(x):', pc)

输出结果为：

PA(x): 3 -> 11 -> 7 -> 8 -> 4 -> 3 -> 5 -> None
PB(x): 8 -> 11 -> 7 -> 8 -> 10 -> 6 -> None
PC(x): 11 -> 11 -> 14 -> 8 -> 10 -> 6 -> 5 -> None

其中，PA(x)、PB(x)、PC(x)分别表示多项式PA、PB、PA+PB的系数和指数。