def reverseKGroup(self, head, k):
if k < 2:
return head
fh = ListNode(0)
fh.next = head
pre, cur = fh, head
while cur:
count = 1
while cur.next and count < k:
count += 1
cur = cur.next
if count < k:
break
before = pre.next
pre.next = cur
pre = before
after = before.next
pre.next = cur.next
while before != cur:
t = after.next
after.next = before
before = after
after = t
cur = pre.next
return fh.next
def swapPairs(self, head):
pre = ListNode(0)
pre.next = head
cur = head
head = pre
while cur and cur.next:
pre.next = cur.next
cur.next = pre.next.next
pre.next.next = cur
pre = cur
cur = cur.next
return head.next
def deleteDuplicates(self, head):
fh = ListNode(0)
fh.next = head
pre, cur = fh, head
while cur:
after = cur.next
while after and after.val == cur.val:
after = after.next
if after == cur.next:
pre = cur
else:
pre.next = after
cur = after
return fh.next
def insertionSortList(self, head):
if not head:
return head
fh = ListNode(0)
fh.next = head
cur = head
while cur.next:
if cur.next.val < cur.val:
pre = fh
while pre.next.val < cur.next.val:
pre = pre.next
t = cur.next
cur.next = t.next
t.next = pre.next
pre.next = t
else:
cur = cur.next
return fh.next
def reverseBetween(self, head, m, n):
if m == n:
return head
fh = ListNode(0)
fh.next = head
pre, cur = fh, head
count = 1
while count < m:
pre = cur
cur = cur.next
count += 1
t, h = cur, cur
cur = cur.next
while count < n:
after = cur.next
cur.next = h
h = cur
cur = after
count += 1
pre.next = h
t.next = cur
return fh.next
def swapNodes(self, head: ListNode, k: int) -> ListNode:
dummy = ListNode()
dummy.next = head
total = 0
cur = dummy
while cur.next:
cur = cur.next
total += 1
lfast, lslow = head, dummy
c = k - 1
while c:
lfast = lfast.next
lslow = lslow.next
c -= 1
rfast, rslow = head, dummy
c = total - k
while c:
rfast = rfast.next
rslow = rslow.next
c -= 1
if lfast.next == rfast:
rnext = rfast.next
lslow.next = rfast
rfast.next = lfast
lfast.next = rnext
elif rfast.next == lfast:
lnext = lfast.next
rslow.next = lfast
lfast.next = rfast
rfast.next = lnext
else:
lnext = lfast.next
rnext = rfast.next
lslow.next = rfast
rfast.next = lnext
rslow.next = lfast
lfast.next = rnext
return dummy.next
