def addTwoNumbers(self, l1: ListNode, l2: ListNode) -> ListNode:
if l1 is None and l2 is None:
return None
pre = result = ListNode(0)
pl = 0
while l1 is not None:
if l2 is not None:
temp = l1.val + l2.val
l2 = l2.next
else:
temp = l1.val
div, mod = divmod(temp + pl, 10)
result.next = ListNode(mod)
pl = div
l1 = l1.next
result = result.next
while l2 is not None:
div, mod = divmod(l2.val + pl, 10)
result.next = ListNode(mod)
pl = div
l2 = l2.next
result = result.next
if pl != 0:
result.next = ListNode(pl)
return pre.next
def mergeTwoLists3(self, l1: ListNode, l2: ListNode) -> ListNode:
if l1 is None:
return l2
elif l2 is None:
return l1
elif l1.val < l2.val:
l1.next = self.mergeTwoLists3(l1.next, l2)
return l1
else:
l2.next = self.mergeTwoLists3(l2.next, l1)
return l2
def removeElements(self, head: ListNode, val: int) -> ListNode:
if head is None:
return None
cur = ListNode(0)
cur.next = head
res = cur
while cur.next:
if cur.next.val == val:
cur.next = cur.next.next
else:
cur = cur.next
return res.next
def removeNthFromEnd(self, head: ListNode, n: int) -> ListNode:
if head is None:
return None
res = ListNode(0)
res.next = head
l1 = res
l2 = res
for i in range(n):
l1 = l1.next
while l1.next:
l1 = l1.next
l2 = l2.next
l2.next = l2.next.next
return res.next
def reverseList_re(self, head: ListNode) -> ListNode:
if head is None or head.next is None:
return head
r = self.reverseList_re(head.next)
head.next.next = head
head.next = None
return r
def mergeTwoLists2(self, l1: ListNode, l2: ListNode) -> ListNode:
head = ListNode(0)
cur = head
cur1 = l1
cur2 = l2
while cur1 and cur2:
if cur1.val <= cur2.val:
cur.next = cur1
cur1 = cur1.next
else:
cur.next = cur2
cur2 = cur2.next
cur = cur.next
if cur1:
cur.next = cur1
if cur2:
cur.next = cur2
return head.next
if head is None or head.next is None:
return head
fast = head
slow = head
while fast.next is not None and fast.next.next is not None:
fast = fast.next.next
slow = slow.next
if fast.next:
return slow.next # 偶数，选第二个
else:
return slow
def middleNode2(self, head: ListNode) -> ListNode:
if head is None or head.next is None:
return head
fast = head
slow = head
while fast and fast.next:
fast = fast.next.next
slow = slow.next
return slow.val
if __name__ == '__main__':
head = ListNode(1)
head.next = ListNode(2)
head.next.next = ListNode(3)
head.next.next.next = ListNode(4)
# head.next.next.next.next = ListNode(5)
print(Solution().middleNode2(head))
链表的倒数第k个结点
"""
from tencent.linkedlist.ListNode import ListNode
class Solution:
def getKthFromEnd(self, head: ListNode, k: int) -> ListNode:
if head is None or k == 0:
return None
fast = head
slow = head
for i in range(k):
if fast:
fast = fast.next
else:
return None # 长度 < k
while fast:
fast = fast.next
slow = slow.next
return slow
if __name__ == '__main__':
head = ListNode(1)
# head.next = ListNode(2)
# head.next.next = ListNode(3)
# head.next.next.next = ListNode(4)
# head.next.next.next.next = ListNode(5)
print(Solution().getKthFromEnd(head, 2))
def addTwoNumbers2(self, l1: ListNode, l2: ListNode) -> ListNode:
if l1 is None or l2 is None:
return None
len_l1, len_l2 = 0, 0
tmp_l1, tmp_l2 = l1, l2
while tmp_l1:
tmp_l1 = tmp_l1.next
len_l1 += 1
while tmp_l2:
tmp_l2 = tmp_l2.next
len_l2 += 1
if len_l1 < len_l2:
l1, l2 = l2, l1
up = 0
head = ListNode(0)
i = 0
while l2:
res = l1.val + l2.val + up
up = 0
if res >= 10:
up, cur = divmod(res, 10)
else:
cur = res
if i == 0:
result = ListNode(cur)
head.next = result
i += 1
else:
result.next = ListNode(cur)
result = result.next
l1 = l1.next
l2 = l2.next
while l1:
res = l1.val + up
up = 0
up, cur = divmod(res, 10)
result.next = ListNode(cur)
result = result.next
l1 = l1.next
if up != 0:
result.next = ListNode(up)
return head.next
if i == 0:
result = ListNode(cur)
head.next = result
i += 1
else:
result.next = ListNode(cur)
result = result.next
l1 = l1.next
l2 = l2.next
while l1:
res = l1.val + up
up = 0
up, cur = divmod(res, 10)
result.next = ListNode(cur)
result = result.next
l1 = l1.next
if up != 0:
result.next = ListNode(up)
return head.next
if __name__ == '__main__':
root = ListNode(1)
# root.next = ListNode(4)
# root.next.next = ListNode(3)
root2 = ListNode(9)
root2.next = ListNode(9)
# root2.next.next = ListNode(4)
print(Solution().addTwoNumbers2(root, root2))
移除链表元素
"""
from tencent.linkedlist.ListNode import ListNode
class Solution:
def removeElements(self, head: ListNode, val: int) -> ListNode:
if head is None:
return None
cur = ListNode(0)
cur.next = head
res = cur
while cur.next:
if cur.next.val == val:
cur.next = cur.next.next
else:
cur = cur.next
return res.next
if __name__ == '__main__':
root = ListNode(6)
root.next = ListNode(2)
root.next.next = ListNode(6)
root.next.next.next = ListNode(4)
root.next.next.next.next = ListNode(5)
root.next.next.next.next.next = ListNode(6)
print(Solution().removeElements(root, 6))
def mergeTwoLists(self, l1: ListNode, l2: ListNode) -> ListNode:
result = ListNode(0)
self.merge(l1, l2, result)
return result.next
class Solution:
def reverseList_re(self, head: ListNode) -> ListNode:
if head is None or head.next is None:
return head
r = self.reverseList_re(head.next)
head.next.next = head
head.next = None
return r
# 构造一个None，然后将所有的node移到
def reverseList(self, head: ListNode) -> ListNode:
if head is None or head.next is None:
return head
pre = None
cur = head
while cur != None:
temp = cur.next
cur.next = pre
pre = cur
cur = temp
return pre
if __name__ == '__main__':
root = ListNode(1)
root.next = ListNode(2)
root.next.next = ListNode(3)
root.next.next.next = ListNode(4)
root.next.next.next.next = ListNode(5)
print(Solution().reverseList(root))
Date： 2020/3/19
https://leetcode-cn.com/explore/interview/card/tencent/222/linked-list/916/
链表是否有环
"""
from tencent.linkedlist.ListNode import ListNode
class Solution:
def hasCycle(self, head: ListNode) -> bool:
if head is None or head.next is None:
return False
fast = head
slow = head
while True:
if fast.next is not None and fast.next.next is not None:
fast = fast.next.next
slow = slow.next
else:
return False
if slow == fast:
return True
if __name__ == '__main__':
root = ListNode(1)
root.next = ListNode(2)
print(Solution().hasCycle(root))