leetcode 82& 21

# Definition for singly-linked list.
# class ListNode:
#     def __init__(self, x):
#         self.val = x
#         self.next = None

class Solution:
    def deleteDuplicates(self, head: ListNode) -> ListNode:

        # 编程时，如果nex可以省略，比如总是和cur是相邻的，可以不定义出来，以免后续cur最后，nex为None，nex.next报错
        # and和or条件计算时，具有短路效应，具体表现为：and左边为False后，不再计算右边，不进入循环
        # or 左边为True后，不计算右边，直接进入循环
        dummy = ListNode(-1)
        dummy.next = head
        pre = dummy
        cur = head
        while cur:
            while cur.next and cur.val == cur.next.val:
                cur = cur.next   
            if pre.next == cur:
                pre = cur
            else:
                pre.next = cur.next
            cur = cur.next
        return dummy.next

  
 

  
1
  
2
  
3
  
4
  
5
  
6
  
7
  
8
  
9
  
10
  
11
  
12
  
13
  
14
  
15
  
16
  
17
  
18
  
19
  
20
  
21
  
22
  
23
  
24
  
25
 

# Definition for singly-linked list.
# class ListNode:
#     def __init__(self, x):
#         self.val = x
#         self.next = None

class Solution:
    def mergeTwoLists(self, l1: ListNode, l2: ListNode) -> ListNode:
        dummy = ListNode(-1)
        cur = dummy
        while l1 and l2:
            if l1.val < l2.val:
                cur.next = l1
                l1 = l1.next
            else:
                cur.next = l2
                l2 = l2.next
            cur = cur.next
        
        while l1:
            cur.next = l1
            l1 = l1.next
            cur = cur.next
        while l2:
            cur.next = l2
            l2 = l2.next
            cur = cur.next
        return dummy.next

  
 

  
1
  
2
  
3
  
4
  
5
  
6
  
7
  
8
  
9
  
10
  
11
  
12
  
13
  
14
  
15
  
16
  
17
  
18
  
19
  
20
  
21
  
22
  
23
  
24
  
25
  
26
  
27
  
28
 

文章来源: blog.csdn.net，作者：weixin_43178406，版权归原作者所有，如需转载，请联系作者。

原文链接：blog.csdn.net/weixin_43178406/article/details/88032116