[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;
}