Remove Nth Node From End of List

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.

方法

使用两个指针进行标记。

	    public ListNode removeNthFromEnd(ListNode head, int n) {
	        ListNode p1 = head;
	        ListNode p2 = head;
	        for(int i = 0; i < n; i ++){
	            p2 = p2.next;
	        }
	        if(p2 == null){
	            head = head.next;
	        }else{
	            while(p2.next != null){
	                p1 = p1.next;
	                p2 = p2.next;
	            }
	             p1.next = p1.next.next;
	        }  
	        return head;
	    }