题解 | #链表中倒数最后k个结点#

import java.util.*;

/*
 * public class ListNode {
 *   int val;
 *   ListNode next = null;
 *   public ListNode(int val) {
 *     this.val = val;
 *   }
 * }
 */

public class Solution {
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     * 
     * @param pHead ListNode类 
     * @param k int整型 
     * @return ListNode类
     */
    public ListNode FindKthToTail (ListNode pHead, int k) {
        // write code here
	  	//用栈来解决
        ListNode listNode = null;
        Stack<ListNode> stack = new Stack<>();
	    //n
        while(pHead!=null){
            stack.push(pHead);
            pHead = pHead.next;
        }
	    //k
        for(int i=0;i<k;i++){
            if(stack.isEmpty()){
                listNode = null;
                break;
            }
            listNode = stack.pop();
        }
	    //时间复杂度O(n+k)=O(n)
        return listNode;
    }
}