思路： 定义fast 和 slow ，先让fast走k-1步，然后再让slow和fast同时走1步，最后得到的slow就是所求的值
代码示例
代码语言：javascript复制lass ListNode {
public int val;
public ListNode next;
public ListNode(int val){
this.val = val;
this.next = null;
}
}
public class TestDemo1025_1 {
public ListNode head;
public ListNode findLastK(int k){
if (k <= 0 ){
System.out.println("不合法");
return null;
}
ListNode fast = this.head;
ListNode slow = this.head;
while (k-1 != 0){
if (fast.next != null){
fast = fast.next;
k--;
}else {
System.out.println("没有这个节点");
return null;
}
}
while (fast.next != null){
slow = slow.next;
fast = fast.next;
}
return slow;
}
}
