237. Delete Node in a Linked List

Question:

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.

Solution(Linked List): 

According to the question: delete a node (except the tail).
O(1).

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) {
        node->val = node->next->val;
        node->next = node->next->next;
    }
};

Solution:

Shifting the remaining portion of the giving linked list to left by one node. Take the tail into consideration.
O(n).

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) {
        ListNode* p1 = node;
        ListNode* p2 = node->next;
        while(p2->next != NULL){
            p1->val = p2->val;
            p1 = p2;
            p2 = p2->next;
        }
        p1->val = p2->val;
        p1->next = NULL;
    }
};