算法1

快慢指针

用上快慢指针，你将拥有一切

Java 代码

class Solution {
    public ListNode findKthToTail(ListNode head, int k) {
        if(head==null||k>ListNodeLong(head))
            return null;

        ListNode fast = head;
        ListNode slow = head;
        int i = 0;
        while(i<k&&fast!=null){
            fast = fast.next;
            i++;
        }

        while(fast!=null){
            fast = fast.next;
            slow = slow.next;
        }

        return slow;
    }

    public int ListNodeLong(ListNode head){
        int count = 0;
        ListNode node = head;
        while(node!=null){
            node = node.next;
            count++;
        }
        return count;
    }
}