def mergeTwoLists(self, l1, l2):
"""
:type l1: ListNode
:type l2: ListNode
:rtype: ListNode
"""
# 方法一：递归
# if not l1:
# return l2
# if not l2:
# return l1
#
# p = ListNode(None)
# if l1.data < l2.data:
# p = l1
# p.next = self.mergeTwoLists(l1.next, l2)
# else:
# p = l2
# p.next = self.mergeTwoLists(l1, l2.next)
# return p
# 方法二：循环
p_head = p = ListNode(0)
while l1 and l2:
if l1.data < l2.data:
p.next = l1
l1 = l1.next
else:
p.next = l2
l2 = l2.next
p = p.next
p.next = l1 or l2
return p_head.next
def reverse_list(head):
if head is None or head.next is None:
return
p_node = head.next
p_pre = None
p_res = None
while p_node is not None:
p_next = p_node.next
if p_next is None:
p_res = ListNode(None)
p_res.next = p_node
p_node.next = p_pre
p_pre = p_node
p_node = p_next
return p_res
def removeNthFromEnd(self, head, n):
"""
:type head: ListNode
:type n: int
:rtype: ListNode
"""
# 分三种情况：
# 1，待删除结点是非头非尾结点（一般情况，即 n > 1）
# 2，待删除结点是长度大于1的链表的尾节点（即n == 1）
# 3，待删除结点是长度等于1的链表的尾节点（也即头节点, n == 1）
# 针对1，则先让i走k-1，ij再同时走直到i走到尾，则j指向待删除结点，利用后一元素覆盖法直接删去即可
# 针对2，此时无法使用后一元素覆盖法，只能用前驱去删，因此需要让j走到待删元素的前驱处，因此在初始时让j位于i前驱处即可
# 针对3，则需将头结点修改为空
if not head or n <= 0:
return head
if n == 1:
pi = head
pj = ListNode(0)
pj.next = head
else:
pj = pi = head
for i in range(n - 1):
if pi:
pi = pi.next
else:
return head
while pi.next:
pi = pi.next
pj = pj.next
if n == 1 and head == pi:
return None
if n == 1:
pj.next = pj.next.next
else:
pj.data = pj.next.data
pj.next = pj.next.next
return head
q = head2 if l2 <= l1 else head1
for i in range(abs(l1 - l2)):
p = p.next
while p and q and p != q:
if p == q:
return q.data
p = p.next
q = q.next
return -1
if __name__ == '__main__':
# test
list1_head = ListNode(None)
for i in range(0, 14, 2):
p = ListNode(i)
add_node(list1_head, p)
list2_head = ListNode(None)
for i in range(1, 11, 3):
p = ListNode(i)
add_node(list2_head, p)
p = ListNode(13)
add_node(list1_head, p)
add_node(list2_head, p)
for i in range(0, 4, 2):
p = ListNode(i)
# 方法二：循环
p_head = p = ListNode(0)
while l1 and l2:
if l1.data < l2.data:
p.next = l1
l1 = l1.next
else:
p.next = l2
l2 = l2.next
p = p.next
p.next = l1 or l2
return p_head.next
if __name__ == '__main__':
head1 = ListNode(None)
head2 = ListNode(None)
for i in range(0, 10, 2):
node = ListNode(i)
add_node(head1, node)
for i in range(1, 11, 2):
node = ListNode(i)
add_node(head2, node)
print_list(head1)
print_list(head2)
print('-----------------')
p = Solution().mergeTwoLists(head1.next, head2.next)
p_pre = None
p_res = None
while p_node is not None:
p_next = p_node.next
if p_next is None:
p_res = ListNode(None)
p_res.next = p_node
p_node.next = p_pre
p_pre = p_node
p_node = p_next
return p_res
if __name__ == '__main__':
head = ListNode(None)
for i in range(4):
node = ListNode(i)
add_node(head, node)
print_list(head)
print('-----------------')
after_reverse_head = reverse_list(head)
print_list(after_reverse_head)
return head
while pi.next:
pi = pi.next
pj = pj.next
if n == 1 and head == pi:
return None
if n == 1:
pj.next = pj.next.next
else:
pj.data = pj.next.data
pj.next = pj.next.next
return head
if __name__ == '__main__':
head = ListNode(None)
for i in range(1):
node = ListNode(i + 1)
add_node(head, node)
print_list(head)
print('-----------------')
p = Solution().removeNthFromEnd(head.next, 1)
new_head = ListNode(None)
new_head.next = p
print_list(new_head)
if head1 is None:
return head2
if head2 is None:
return head1
p = head1 if head1.data < head2.data else head2
p.next = merge_list(head1.next,
head2) if head1.data < head2.data else merge_list(
head1, head2.next)
return p
if __name__ == '__main__':
list1_head = ListNode(None)
for i in range(0, 10, 2):
p = ListNode(i)
add_node(list1_head, p)
list2_head = ListNode(None)
for i in range(1, 11, 2):
p = ListNode(i)
add_node(list2_head, p)
print_list(list1_head)
print_list(list2_head)
print('-------------')
new_head = ListNode(None)