判断链表是否是一个回文结构

    // 用栈的方法,把链表放入栈中，再弹出来同时打印对应链表值对比看是否相等
    public static Boolean IsHuiWen(Node head){
        if(head == null || head.next == null){
            return true;
        }
        Node temp =head;
        Stack<Node> stack = new Stack<>(); 
        // 链表 入栈
        while(temp != null){
            stack.push(temp);
            temp = temp.next;
        }
        while(!stack.isEmpty()){
            Node pop = stack.pop();
            if(pop.value != head.value){
                return false;
            }
            head = head.next;
        }
        return true;
    }
    // 用快慢指针找出中点，一半部分入栈
    public static Boolean isHuiWen2(Node head){
        if(head == null || head.next == null){
            return true;
        }
        // 快慢指针，快指针结束后，慢指针就在中点
        Node slow = head;
        Node fast = head;
        while(slow.next != null && fast.next.next != null){
            slow = slow.next;
            fast = fast.next.next;
        }
        Stack<Node> stack = new Stack<>();
        while(slow != null){
            stack.push(slow);
            slow = slow.next;
        }
        while(!stack.isEmpty()){
            if(stack.pop().value != head.value){
                return false;
            }
            head = head.next;
        }
        return true;
    }