题解 | #反转链表#

import java.util.*;

public class Solution {
    public ListNode ReverseList(ListNode head) {

        Stack<Integer> stack = new Stack<>();

        while (head != null) {
            stack.push(head.val);
            head = head.next;
        }

        if (stack.isEmpty()) {
            return null;
        }

        ListNode r =  new ListNode(stack.pop());

        ListNode p = r;

        while (!stack.isEmpty()) {
            r.next = new ListNode(stack.pop());
            r = r.next;
        }

        r.next = null;

        return p;
    }
}