leetcode 19. Remove Nth Node From End of List

//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.


public class Solution {
	
	static class ListNode {
	      int val;
	      ListNode next;
	      ListNode(int x) { val = x; }
	}
	
	public static void main(String[] args) {
		ListNode a = new ListNode(1);
		ListNode input = a;
		for(int i = 0;i<1;i++){
			ListNode temp = new ListNode(i+2);
			a.next = temp;
			a = a.next;
		}
		ListNode result = removeNthFromEnd(input,2);
		
		while(result != null){
			System.out.println(result.val);
			result = result.next;
		}
	}
	
	public static ListNode removeNthFromEnd(ListNode head, int n) {
        ListNode result = head;
        int count = 1;
		while(head.next!=null){									//        
        	count++;
        	head = head.next;
        }
		if(count == 1){											//       ，   
			return null;
		}
		int timing = count-n;
		if(timing == 0){										//      0，           
			result = result.next;
			return result;
		}
		head = result;
		for(int i = 1;i<timing;i++){							//        
			head = head.next;
		}
		head.next = head.next.next;								//            
        return result;
    }
	
}