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：

　　先考慮特殊情況：（1）鏈表為空（2）只有一個節點 -- 都直接返回

　　普通情況：鏈表不為空，且後續節點也不為空

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     struct ListNode *next;
 * };
 */
void deleteNode(struct ListNode* node) {
    if (!node)  //鏈表不為空
        return;
    else if (node->next){  //要刪的節點還有後續節點
        node->val = node->next->val;
        node
 
->next = node->next->next;
    }
    else  //其他情況，如列表不為空且要刪除的是最後一個節點
        return;
}

237. Delete Node in a Linked List