Leetcode linked list class

206 topic ： Reverse a linked list

Method 1 ： Double finger needling

class Solution(object):
    def reverseList(self, head):
        pre=None
        cur=head
        while(cur!=None):
            temp=cur.next
            cur.next=pre
            pre=cur
            cur=temp
        return pre # Return to header node 

203 topic ： Remove linked list elements

How to delete a linked list element
1） Directly use the original linked list to delete the operation .
Delete header node ： Head node moves backward by one bit , It needs to be written separately
2） Set another virtual head node , The pointer cur Start traversing the linked list from the virtual head node .

# Virtual head node method 
class Solution(object):
    def removeElements(self, head, val):
        dummy_head=ListNode(next=head)# Set the virtual header node 
        cur=dummy_head
        while(cur.next!=None):
            if(cur.next.val==val):
                cur.next=cur.next.next
            else:
                cur=cur.next
        return dummy_head.next