leetcode Question:Delete Node in a Linked List

Delete Node in a Linked List

Write a function to delete a node (except the tail) in a singly linked list, given only access to that node.

Supposed the linked list is 1 -> 2 -> 3 -> 4 and you are given the third node with value 3, the linked list should become 1 -> 2 -> 4 after calling your function.

Analysis:

To solve this problem, the key point is "overwrite" !

Usually we are thinking "skip" the node we want to delete by:
1 -> 2 -> 3 -> 4 -> Null, delete 3, we have:
1 -> 2--------> 4 -> Null.

However in this problem, the previous node is unknown.
So, what we should do is to overwrite the node  "3" by node "4":
1 -> 2 -> 3 -> 4->Null, delete 3, we have:
1 -> 2 -> 4->Null.

Just pay attention to the case that the node is the last node.

Code(C++):

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}
 * };
 */
class Solution {
public:
    void deleteNode(ListNode* node) {
        if (node->next){
            node->val = node->next->val;
            node->next = node->next->next;
        }else{
            node = NULL;
        }
    }
};

Code(Python):

# Definition for singly-linked list.
# class ListNode(object):
#     def __init__(self, x):
#         self.val = x
#         self.next = None

class Solution(object):
    def deleteNode(self, node):
        """
        :type node: ListNode
        :rtype: void Do not return anything, modify node in-place instead.
        """
        if node.next:
            node.val = node.next.val
            node.next = node.next.next
        else:
            node = None