【剑指offer】输出链表倒数第K个元素

/*
public class ListNode {
    int val;
    ListNode next = null;

    ListNode(int val) {
        this.val = val;
    }
}*/
public class Solution {
    public ListNode FindKthToTail(ListNode head,int k) {
        if(head == null) return null;
        int length = 0;
        ListNode tempNode = head;
        ListNode result;
        while(tempNode!=null){
            length++;
            tempNode = tempNode.next;
        }
        //判断K值是否合法
        if(k > length) return null;
        tempNode = head;
        for(int i=0; i<length; i++){
            if(i>=k){
                head = head.next;
            }
            tempNode  = tempNode.next;
        }
        return head;
    }
}