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.
常规方法是修改该节点前面的那个节点。由于只能访问当前节点，且当前节点不是最末尾的节点，可以放心的把其 next 节点的值拷贝过来，并修改其 next 节点。
class Solution {
public void deleteNode(ListNode node) {
node.val = node.next.val;
node.next = node.next.next;
}
}