[leetcode 19] Remove Nth Node From End of List

1 题目

Given a linked list, remove the nth node from the end of list and return its head.

For example,

   Given linked list: 1->2->3->4->5, and n = 2.

   After removing the second node from the end, the linked list becomes 1->2->3->5.

Note:
Given n will always be valid.
Try to do this in one pass.

2 思路

题目要求遍历一遍搞定，那么，就可以用两个指针，先第一个先往前走N个，然后再一起走，最后，移除后一个元素。自己做出来的。。

3 代码

        public ListNode removeNthFromEnd(ListNode head, int n) {
            ListNode node = head;
            while(n>0 && node!=null){
                node = node.next;
                n--;
            }
            ListNode start = head;
            if(node != null){
                while(node.next != null){
                    node = node.next;
                    start = start.next;
                }
            }else{
                /* will remove the first object */
                start = start.next;
                return start;
            }
            
            start.next = start.next.next;
            return head;
        }