CODEWITHSUNDEEP
python
Roger Josh
Roger Josh

Reputation: 507

Deleting node from a singly linked list (except for the tail)

I'm a beginner to programming and I'm trying to understand the following code:

    # class ListNode(object):
    #     def __init__(self, x):
    #         self.val = x
    #         self.next = None

    class Solution(object):
        def deleteNode(self, node):
            node.val = node.next.val
            node.next = node.next.next

My intuition for the code is the following: I understand that node is a reference to an element in the linked list and node.next is a pointer to the next node. I also understand that node.val sets the value of the current node to the value of the next node. What exactly is the purpose of 

    node.next = node.next.next?

Upvotes: 0

Views: 56

Answers (3)

Chad S.
Chad S.

Reputation: 6633

Imagine the following linked list nodes (where n2 is the node you're removing)

... -> n1 -> n2 -> n3 -> ...
 node -^     ^     ^- node.next.next
             |
     node.next

So if you set node.next = node.next.next you get this:

             n2
             |
             v
... -> n1 -> n3 -> ...
 node -^     ^     
             |      
     node.next

And since now nothing is referring to n2 once the function returns it will be garbage collected.

Upvotes: 3

ᴀʀᴍᴀɴ
ᴀʀᴍᴀɴ

Reputation: 4528

It means that the link to next node is removed and this node links to next.next node , it means the next node is deleted and its value replace with this node value. for example we have following list:

1->2->3->4
1.next(2) = 1.next.next(3)

so list updatedt to:

1->3->4

Upvotes: 1

LiamG
LiamG

Reputation: 68

NodeA -> NodeB -> NodeC

So currently NodeA.next is NodeB

by assinging NodeA.next = NodeA.next.next we get NodeA.next = NodeB.next which makes

NodeA.next = NodeC

so the chain is now

NodeA -> NodeC

Upvotes: 2

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