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.

思路：因為只給了當前結點(except the tail)，只能替換成下一個結點的值再delete掉下一個。
1a: direct deletion
1b: with garbage collection

Time Complexity: O(1) Space Complexity: O(1)

Solution1a Code：

class Solution {
    public void deleteNode(ListNode node) {
        node.val = node.next.val;
        node.next = node.next.next;
    }
}

Solution1b Code：

class Solution {
    public void deleteNode(ListNode node) {
        ListNode save_next = node.next.next;
        node.val = node.next.val;
        node.next = null;
        node.next = save_next;
    }
}