def swapPairs(self, head):
# write your code here
if not head or head.next is None: return head
dummyNode = ListNode(0)
dummyNode.next = head
while head.next is not None:
tmp = head.next
head.next = head.next.next
tmp.next = head
head = head.next
return dummyNode.next
def removeNthFromEnd(self, head, n):
# write your code here
cur = head
dummy = ListNode(0)
dummy.next = head
pre = dummy
for i in range(1, n + 1):
head = head.next
while head is not None:
head = head.next
cur = cur.next
pre = pre.next
pre.next = cur.next
return dummy.next
def swapPairs2(self, head):
dummy = ListNode(0)
left = dummy
dummy.next = head
mid = head
right = head.next
while right.next is not None:
mid.next = right.next
right.next = mid
left.next = right
left = left.next.next
mid = mid.next
right = mid.next
return dummy.next
def findMid(self, head):
if not head: return None
if head.next is None: return head
if head.next.next is None: return head
dummy = ListNode(0)
dummy.next = head
pre = dummy
cur = head
while head is not None and head.next is not None:
head = head.next.next
cur = cur.next
pre = pre.next
if head is None: return pre
return cur
def deleteDuplicates2(self, head):
if head == None: return None
dummyNode = ListNode(0)
dummyNode.next = head
pre = dummyNode
while head != None:
if head.next != None and head.val == head.next.val:
while head.next != None and head.val == head.next.val:
head = head.next
pre.next = head.next
head = head.next
else:
pre = pre.next # or pre=head
head = head.next
return dummyNode.next
def removeElements(self, head, val):
# write your code here
if head == None: return None
dummyNode = ListNode(0)
dummyNode.next = head
pre = dummyNode
# if head.val == val: return dummyNode.next.next
while head is not None:
if head.val == val:
pre.next = head.next
head = head.next
continue
pre = pre.next
head = head.next
return dummyNode.next
def findmid(head):
if not head:
return None
if head.next is None: return head
if head.next.next is None: return head
dummy = ListNode(0)
dummy.next = head
pre = dummy
cur = head
while head is not None and head.next is not None:
head = head.next.next
cur = cur.next
pre = pre.next
if head is None: return pre # enev case
return cur # ods case
def deleteDuplicates(self, head):
# write your code here
if head == None: return None
dummyNode = ListNode(0)
dummyNode.next = head
pre = dummyNode
while head != None:
if head.next != None and head.val == head.next.val:
value = head.val # todo important
while head != None and head.val == value:
head = head.next # todo also
pre.next = head
else:
pre = head
head = head.next
return dummyNode.next
def partition(self, head, x):
# write your code here
if not head: return 0
Leftdummy = ListNode(0)
rightdummy = ListNode(0)
left = Leftdummy
right = rightdummy
while head is not None:
if head.val < x:
left.next = head
left = left.next
else:
right.next = head
right = right.next
head = head.next
right.next = None
left.next = rightdummy.next
return Leftdummy.next
def rotateRight(self, head, k):
# write your code here
if not head: return None
if head.next is None: return head
cur = head
dummy = ListNode(0)
dummy.next = head
pre = head
j = 0
for i in range(1, k + 1):
if head.next is not None:
j += 1
head = head.next
if j <= k: return pre
while head.next is not None:
head = head.next
cur = cur.next
# pre = pre.next
cur.next = None
head.next = pre
return head
def merge(self, start, mid):
i = start
j = mid
dummy = ListNode(0)
dummy.next = start
while not start and not mid:
if start.val < mid.val:
dummy.next = start
start = start.next
else:
dummy.next = mid
mid = mid.next
dummy.next = dummy
return dummy.next
return dummyNode.next
def swap(self, head, pre):
if head.next.next is not None:
head.next = head.next.next
head.next.next = pre
pre = head
self.swap(head.next.next, pre)
# https://mp.weixin.qq.com/s?__biz=MzU0OTU5OTI4MA==&idx=2&mid=2247485084&sn=78dfedad9f8e6840378a60b6c1f0ae4f
# https://leetcode-cn.com/problems/swap-nodes-in-pairs/solution/hua-jie-suan-fa-24-liang-liang-jiao-huan-lian-biao/
def swapPairs2(self, head):
dummy = ListNode(0)
left = dummy
dummy.next = head
mid = head
right = head.next
while right.next is not None:
mid.next = right.next
right.next = mid
left.next = right
left = left.next.next
mid = mid.next
right = mid.next
return dummy.next
s = Solution()
s.swapPairs2(head_with_6ele_repeat4end)
ListNode.printLinklist(head_with_6ele_repeat4end)
dummy.next = start
while not start and not mid:
if start.val < mid.val:
dummy.next = start
start = start.next
else:
dummy.next = mid
mid = mid.next
dummy.next = dummy
return dummy.next
def findMid(self, head):
if not head: return None
if head.next is None: return head
if head.next.next is None: return head
dummy = ListNode(0)
dummy.next = head
pre = dummy
cur = head
while head is not None and head.next is not None:
head = head.next.next
cur = cur.next
pre = pre.next
if head is None: return pre
return cur
s = Solution()
a = s.sortList(head_with_6ele_repeat4end)
ListNode.printLinklist(a)