用LinkList类型自行建立两个有序的单链表，其中使用头插法创建链表 La，使用尾插法创建链表 Lb。将 La 与 Lb合并，得到有序链表 Lc

在Python中，我们可以首先定义一个链表节点类`ListNode`，然后分别用头插法（head insert）和尾插法（tail append）创建两个链表La和Lb。最后，通过比较节点值，合并这两个链表成一个新的有序链表Lc。

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

def build_sorted_list(head, values):
    if not head:
        return ListNode(values[0])
    
    current = head
    for value in values:
        new_node = ListNode(value)
        if current.val > value:
            new_node.next = current
            current = new_node
        else:
            while current.next and current.next.val < value:
                current = current.next
            current.next = new_node
    return head

# 创建头插法链表La
values_la = [1, 3, 5, 7]
la_head = None
for value in values_la:
    la_head = build_sorted_list(la_head, [value])

# 创建尾插法链表Lb
values_lb = [2, 4, 6, 8]
lb_tail = None
for value in values_lb:
    lb_tail = build_sorted_list(build_sorted_list(lb_tail, [value]), [value])

# 合并两个链表Lc
lc_head = la_head
while lc_head and lb_tail:
    if lc_head.val <= lb_tail.val:
        lc_head.next = lb_tail
        if lb_tail.next:
            lb_tail = lb_tail.next
        else:
            break
    else:
        lc_head = lc_head.next
if lb_tail:
    lc_head.next = lb_tail

# 输出合并后的链表Lc
current = lc_head
while current:
    print(current.val, end=" -> ")
    current = current.next
print("None")