链表中倒数第k个节点（剑指offer-14）

 /*

 public class ListNode {

     int val;

     ListNode next = null;

     ListNode(int val) {

         this.val = val;

     }

 }*/

 public class Solution {

     public ListNode FindKthToTail(ListNode head,int k) {

         ListNode P2 = head;//head其实就是P1节点，让P2和P1指向链表开头

         while(k != 0){

             if(P2 == null){//k超出链表长度，直接返回null

                 return null;

             }

             P2 = P2.next;

             k--;

         }

         while(P2 != null){//同时移动P1和P2

             P2 = P2.next;

             head = head.next;

         }

         return head;

     }

 }