剑指 Offer 22. 链表中倒数第k个节点

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) { val = x; }
 * }
 */
 //双指针法，2个指针遍历链表，其中一个先走 k-1 步，然后2个指针一起走，当先走的指针指向空，结束
class Solution {
    public ListNode getKthFromEnd(ListNode head, int k) {
        //判空
        if(head == null){
            return null;
        }
        ListNode front = head,later = head;
        //front 先走
        for(int i = 0;i < k;i++){
            front = front.next;
        }
        //一起走
        while(front != null){
            front = front.next;
            later = later.next;
        }
        return later;
    }
}