資料結構 - java翻轉鍊錶是如何實現的?

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;


    }

這段程式碼while循環中他是如何翻轉的?想要詳細一點的,debug了幾次還是沒弄懂具體是怎麼回事

Answer 1

參考一下，理解目的就比較好理解了。容易混亂的地方就是從右往左來處理，因為得先把後面的東西存起來，不然被覆蓋掉就丟了。

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

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

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

Answer 2

Ps:建議先多了解一下鍊錶