203.移除链表元素
竟然可以做个假head，学到了
class ListNode(object):
def __init__(self, val=0, next=None):
self.val = val
self.next = next
class Solution(object):
def removeElements(self, head, val):
dummy_head = ListNode(-1)
dummy_head.next = head
current_node = dummy_head
while current_node.next != None:
if current_node.next.val == val:
current_node.next = current_node.next.next
else:
current_node = current_node.next
return dummy_head.next
707.设计链表
206.反转链表
class ListNode(object):
def __init__(self, val=0, next=None):
self.val = val
self.next = next
class Solution(object):
def reverseList(self, head):
tailNode = None
newNode = None
while head:
newNode = ListNode(head.val, tailNode)
tailNode = newNode
head = head.next
return newNode
If save space:
class Solution(object):
def reverseList(self, head):
# Initialize prev pointer as NULL...
prev = None
# Initialize the curr pointer as the head...
curr = head
# Run a loop till curr points to NULL...
while curr:
# Initialize next pointer as the next pointer of curr...
next = curr.next
# Now assign the prev pointer to curr’s next pointer.
curr.next = prev
# Assign curr to prev, next to curr...
prev = curr
curr = next
return prev # Return the prev pointer to get the reverse linked list...