Sword refers to offer to brush questions-GZ14-the kth node from the bottom in the linked list

Title description
Input a linked list and output the kth node from the bottom of the linked list.
Example 1
input

1,{1,2,3,4,5}

return value

{5}

method one:

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

    ListNode(int val) {
        this.val = val;
    }
}*/
public class Solution {
    
    
    public ListNode FindKthToTail(ListNode head,int k) {
    
    
        //1.首先定义两个指向链表头的指针p,q;
        //2.让p指针先移动到第k节点，然后两个指针同时后移
        //3.当p指针为null时，q指向的即为倒数第k个节点。返回q
        ListNode p=head, q=head;
        while(p != null){
    
    
            if(k <= 0){
    
    
                q = q.next;
            }
            p = p.next;
            k--;
        }
        return k <= 0 ? q : null;
    }
}

Method 2: Use Stack, push the node into the stack, and then take out the kth one

public class Solution {
    
    
    public ListNode FindKthToTail(ListNode head,int k) {
    
    
		if(head == null || k ==0 ){
    
    
			return null;
		}
		
		//可以先把链表反转，然后找出第k个
		Stack<ListNode> stack = new Stack<ListNode>();
		int count = 0;
		while(head != null){
    
    
			stack.push(head);
			head = head.next;
			count++;
		}
		
		if(count < k){
    
    
			return null;
		}
		
		ListNode knode = null;
		for(int i = 0; i < k; i++){
    
    
			knode = stack.pop();
		}
		
		return knode;
}