def addTwoNumbers(self, l1: ListNode, l2: ListNode) -> ListNode:
st1, st2 = list(), list()
while l1:
st1.append(l1.val)
l1 = l1.next
while l2:
st2.append(l2.val)
l2 = l2.next
tail, c = None, 0
while st1 or st2 or c:
cur = c
if st1:
cur += st1.pop()
if st2:
cur += st2.pop()
c = cur // 10
curNode = ListNode(cur % 10)
curNode.next = tail
tail = curNode
return tail
def reverseKGroup(self, head: ListNode, k: int) -> ListNode:
if not head or not head.next or k <= 1:
return head
dummy = tail = ListNode(0)
while head:
cnt = 1
cur = head
while cur and cnt < k:
cnt += 1
cur = cur.next
if cur:
t = cur.next
cur.next = None
while head:
tt = head.next
head.next = tail.next
tail.next = head
head = tt
while tail.next:
tail = tail.next
head = t
else:
tail.next = head
head = None
return dummy.next
def reverseList(self, head: ListNode) -> ListNode:
dummy = ListNode(0)
while head:
t = head.next
head.next = dummy.next
dummy.next = head
head = t
return dummy.next
def removeNthFromEnd(self, head: ListNode, n: int) -> ListNode:
dummy = ListNode(0)
dummy.next = head
prev = cur = dummy
for i in range(n):
cur = cur.next
while cur.next:
prev = prev.next
cur = cur.next
prev.next = prev.next.next
return dummy.next
def sortList(self, head: ListNode) -> ListNode:
if not head or not head.next:
return head
slow = fast = head
while fast.next and fast.next.next:
slow = slow.next
fast = fast.next.next
rRes = self.sortList(slow.next)
slow.next = None
lRes = self.sortList(head)
dummy = tail = ListNode(0)
while lRes and rRes:
if lRes.val <= rRes.val:
tail.next = lRes
tail = tail.next
lRes = lRes.next
else:
tail.next = rRes
tail = tail.next
rRes = rRes.next
if lRes:
tail.next = lRes
else:
tail.next = rRes
return dummy.next
def reverseListHelper(self, oldHead: ListNode, newHead: ListNode) -> ListNode:
if oldHead:
oldNext = oldHead.next
oldHead.next = newHead
return self.reverseListHelper(oldNext, oldHead)
return newHead
def oddEvenList(self, head: ListNode) -> ListNode:
oddDummy = oddTail = ListNode(0)
evenDummy = evenTail = ListNode(0)
while head:
oddTail.next = head
oddTail = oddTail.next
head = head.next
if head:
evenTail.next = head
evenTail = evenTail.next
head = head.next
oddTail.next = evenDummy.next
evenTail.next = None
return oddDummy.next
def reorderList(self, head: ListNode) -> None:
"""
Do not return anything, modify head in-place instead.
"""
if not head or not head.next:
return head
slow = fast = head
while fast.next and fast.next.next:
slow = slow.next
fast = fast.next.next
fast = slow.next
fast = self.reverseList(fast)
slow.next = None
dummy = tail = ListNode(0)
while head and fast:
tail.next = head
tail = tail.next
head = head.next
tail.next = fast
tail = tail.next
fast = fast.next
tail.next = head
return dummy.next
def insertionSortList(self, head: ListNode) -> ListNode:
if not head or not head.next:
return head
dummy = ListNode(-(1 << 31))
while head:
t = head.next
cur = dummy
while cur.next and cur.next.val <= head.val:
cur = cur.next
head.next = cur.next
cur.next = head
head = t
return dummy.next
def addTwoNumbers(self, l1: ListNode, l2: ListNode) -> ListNode:
dummy = tail = ListNode(0)
c = 0
while l1 or l2 or c:
if l1:
c += l1.val
l1 = l1.next
if l2:
c += l2.val
l2 = l2.next
tail.next = ListNode(c % 10)
tail = tail.next
c //= 10
return dummy.next
def removeElements(self, head: ListNode, val: int) -> ListNode:
dummy = tail = ListNode(0)
while head:
if head.val != val:
tail.next = head
tail = tail.next
head = head.next
tail.next = None
return dummy.next
def mergeTwoLists(self, l1: ListNode, l2: ListNode) -> ListNode:
dummy = tail = ListNode(0)
while l1 and l2:
if l1.val < l2.val:
tail.next = l1
l1 = l1.next
else:
tail.next = l2
l2 = l2.next
tail = tail.next
tail.next = l1 if l1 else l2
return dummy.next
def splitListToParts(self, root: ListNode, k: int) -> List[ListNode]:
n, cur = 0, root
while cur:
n += 1
cur = cur.next
res, cur, avg, ext = list(), root, n // k, n % k
for _ in range(k):
dummy = ListNode(0)
tail = dummy
for _ in range(avg + (ext > 0)):
tail.next = cur
tail = tail.next
cur = cur.next
ext -= 1
tail.next = None
res.append(dummy.next)
return res
def swapPairs(self, head: ListNode) -> ListNode:
if not head or not head.next:
return head
dummy = tail = ListNode(0)
while head:
if head.next:
t = head.next.next
tail.next = head.next
tail = tail.next
tail.next = head
tail = tail.next
head = t
else:
tail.next = head
tail = tail.next
head = None
tail.next = None
return dummy.next
def mergeKLists(self, lists: List[ListNode]) -> ListNode:
if not lists:
return None
dummy = tail = ListNode(0)
# default min heap, sort by the first elem, then second, then ...
pq = PriorityQueue()
for idx, li in enumerate(lists):
if li:
pq.put((li.val, idx, li))
while not pq.empty():
_, idx, cur = pq.get()
tail.next = cur
tail = tail.next
cur = cur.next
if cur:
pq.put((cur.val, idx, cur))
return dummy.next