leetcode -- Insertion Sort List -- 重点，需要优化

思路1

思路2

class Solution(object):
def insertionSortList(self, head):
"""
:type head: ListNode
:rtype: ListNode
"""
if not head:
return head

dummy_node = ListNode(0)
dummy_node.next = head

cur, e = head.next, head #s 是每一次的搜索开始节点，p是previous s. e 是cur的前面那个node
p = dummy_node
while cur:
s, p = dummy_node.next, dummy_node

while s != cur and s.val <= cur.val:
p,s = s, s.next
if s == cur:
e, cur = cur, cur.next
else:
e.next, tmp = cur.next, cur.next
p.next, cur.next = cur, s
cur = tmp
return dummy_node.next