数据结构 - java翻转链表是如何实现的?

Question

public class Node {
    public int value;
    public Node next;

    public Node(int data) {
        this.value = data;
    }


    public Node reverse(Node head) {
        Node pre = null;
        Node next = null;

        while (head != null) {
            next = head.next;
            head.next = pre;
            pre = head;
            head = next;

        }
        return pre;


    }

这段代码while循环中他是如何翻转的?想要详细一点的,debug了几次还是没弄懂具体是怎么回事

Answer 1

参考一下，理解目的就比较好理解了。容易混乱的地方就是从右往左来处理，因为得先把后面的东西存起来，不然被覆盖掉就丢了。

 pre        head       
+----+     +----+  +> +----+
|    |     |    |  |  |    |
|    |     |    |  |  |    |
|    |     |    |  |  |    |
+----+     +----+  |  +----+
|    |     |    |  |  |    |
|    |     |    |  |  |    |
+----+     +-+--+  |  +----+
             |     |
             +-----+

 pre        head       next        next = head.next;
+----+     +----+  +> +----+
|    |     |    |  |  |    |
|    |     |    |  |  |    |
|    |     |    |  |  |    |
+----+     +----+  |  +----+
|    |     |    |  |  |    |
|    |     |    |  |  |    |
+----+     +-+--+  |  +----+
             |     |
             +-----+

 pre        head       next
+----+ <+  +----+     +----+
|    |  |  |    |     |    |
|    |  |  |    |     |    |
|    |  |  |    |     |    |
+----+  |  +----+     +----+
|    |  |  |    |     |    |
|    |  |  |    |     |    |
+----+  |  +-+--+     +----+
        |    |                     head.next = pre;
        +----+
                       next
            pre        head        pre = head;
+----+ <+  +----+     +----+       head = next;
|    |  |  |    |     |    |
|    |  |  |    |     |    |
|    |  |  |    |     |    |
+----+  |  +----+     +----+
|    |  |  |    |     |    |
|    |  |  |    |     |    |
+----+  |  +-+--+     +----+
        |    |
        +----+

Answer 2

Ps:建议先多了解一下链表