C# I'；我无法理解下面的c代码片段

我只有这部分代码。我无法理解“下一步”是ptr的另一种方法还是随机的下一种方法。我只是想知道这是否是专家使用的常见代码片段

Node mystery(Node ptr) {
    Node temp;
    Node previous = null;
    while (ptr != null) {
        temp = ptr.next;
        ptr.next = previous;
        previous = ptr;
        ptr = temp;
    }
    return previous;
}    

---

通常节点对象有一个值（例如int类型）和另一个保存下一个节点的属性

public class Node{
 public int Value {get; set;}
 public Node Next {get; set;}
 //...
}

例如，这里

n1

的下一个节点是

n2

节点

您可以使用调试器或带笔的纸一步一步地执行逻辑

这看起来像是一个大问题。每个节点指向下一个节点，最后一个注释指向

null

head                    tail
+---+       +---+       +---+
|"A"| next  |"B"| next  |"C"| next
|   |------>|   |------>|   |------> null
+---+       +---+       +---+

while（ptr！=null）{

将循环，直到当前节点为

null

head                    tail
+---+       +---+       +---+
|"A"| next  |"B"| next  |"C"| next
|   |------>|   |------>|   |------> null
+---+       +---+       +---+

while范围内的代码是一个典型的交换。让我们一步一步地执行它，因为

ptr

是包含

“a”

的节点，如上所述

temp = ptr.next;

现在，

temp

正在指向下一个节点

 ptr
  |
  v
+---+       +---+       +---+
|"A"| next  |"B"| next  |"C"| next
|   |------>|   |------>|   |------> null
+---+       +---+       +---+
              ^
              |
            temp

---

现在，

ptr.next

指向初始化为空的

previous

。

ptr

现在从列表中取消链接

 ptr
  |
  v
+---+             | +---+       +---+
|"A"| next        | |"B"| next  |"C"| next
|   |------> null | |   |------>|   |------> null
+---+             | +---+       +---+
                  |   ^
                  |   |
                    temp

---

ptr

和

previous

都指向同一节点

 ptr
  |
  v
+---+             | +---+       +---+
|"A"| next        | |"B"| next  |"C"| next
|   |------> null | |   |------>|   |------> null
+---+             | +---+       +---+
  ^               |   ^
  |               |   |
previous             temp

                     ptr
                      |
                      v
+---+             | +---+       +---+
|"A"| next        | |"B"| next  |"C"| next
|   |------> null | |   |------>|   |------> null
+---+             | +---+       +---+
  ^               |   ^
  |               |   |
previous             temp

---

现在，

ptr

和

temp

都指向同一个节点

 ptr
  |
  v
+---+             | +---+       +---+
|"A"| next        | |"B"| next  |"C"| next
|   |------> null | |   |------>|   |------> null
+---+             | +---+       +---+
  ^               |   ^
  |               |   |
previous             temp

                     ptr
                      |
                      v
+---+             | +---+       +---+
|"A"| next        | |"B"| next  |"C"| next
|   |------> null | |   |------>|   |------> null
+---+             | +---+       +---+
  ^               |   ^
  |               |   |
previous             temp

由于

ptr！=null

为真，循环将继续：

temp = ptr.next;

                     ptr
                      |
                      v
+---+             | +---+       +---+
|"A"| next        | |"B"| next  |"C"| next
|   |------> null | |   |------>|   |------> null
+---+             | +---+       +---+
  ^               |               ^
  |               |               |
previous                        temp

---

现在，当前节点的下一项是先前保存的项（A“节点）：

---

---

由于

ptr！=null

为真，循环将继续并应用相同的逻辑：

temp = ptr.next;

                                  ptr
                                   |
                                   v
+---+        +---+             | +---+
|"B"| next   |"A"| next        | |"C"| next
|   |------> |   |------> null | |   |------> null
+---+        +---+          ^  | +---+          ^
  ^                         |  |                |
  |                         |                   |
previous                    +-----------------temp

---

---

---

现在，

while（ptr！=null）

为false。循环结束并返回

previous

，即新头

---

此方法反转链表的顺序并返回标题。

您可以编写反转单个链表的代码

这只是反转单个链接列表的另一个示例： （有关更多详细信息，请参阅）

---

单击

next

，然后点击

F12

。这看起来像是一个非常标准的链表，其中每个

节点

都有一个指向其后一个节点的指针，通常称为

next

next

不能是一个方法-它必须是一个属性，因为您为它指定了一个值it@SirRufo我猜是一个领域：）这看起来就像是在颠倒一个链表？如果是这样的话：当然，它可能偶尔会用到；也不是每天都会用到；老实说，你可能不应该经常编写自己的列表/集合/etc类型

ptr.next = previous;

 ptr
  |
  v
+---+        +---+             | +---+
|"B"| next   |"A"| next        | |"C"| next
|   |------> |   |------> null | |   |------> null
+---+        +---+             | +---+
               ^               |   ^
               |                   |
            previous              temp

previous = ptr;

 ptr
  |
  v
+---+        +---+             | +---+
|"B"| next   |"A"| next        | |"C"| next
|   |------> |   |------> null | |   |------> null
+---+        +---+             | +---+
  ^                            |   ^
  |                                |
previous                         temp

ptr = temp;

                                  ptr
                                   |
                                   v
+---+        +---+             | +---+
|"B"| next   |"A"| next        | |"C"| next
|   |------> |   |------> null | |   |------> null
+---+        +---+             | +---+
  ^                            |   ^
  |                                |
previous                         temp

temp = ptr.next;

                                  ptr
                                   |
                                   v
+---+        +---+             | +---+
|"B"| next   |"A"| next        | |"C"| next
|   |------> |   |------> null | |   |------> null
+---+        +---+          ^  | +---+          ^
  ^                         |  |                |
  |                         |                   |
previous                    +-----------------temp

ptr.next = previous;

 ptr
  |
  v
+---+        +---+        +---+
|"C"| next   |"B"| next   |"A"| next
|   |------> |   |------> |   |------> null
+---+        +---+        +---+          ^
               ^                         |
               |                         |
           previous                     temp

previous = ptr;

 ptr
  |
  v
+---+        +---+        +---+
|"C"| next   |"B"| next   |"A"| next
|   |------> |   |------> |   |------> null
+---+        +---+        +---+         ^
  ^                                     |
  |                                     |
previous                               temp

ptr = temp;

                                       ptr
                                        |
+---+        +---+        +---+         |
|"C"| next   |"B"| next   |"A"| next    v
|   |------> |   |------> |   |------> null
+---+        +---+        +---+         ^
  ^                                     |
  |                                     |
previous                               temp

// C# program for reversing the linked list 
using System; 

class GFG { 
    static void Main(string[] args) 
    { 
        LinkedList list = new LinkedList(); 
        list.AddNode(new LinkedList.Node(85)); 
        list.AddNode(new LinkedList.Node(15)); 
        list.AddNode(new LinkedList.Node(4)); 
        list.AddNode(new LinkedList.Node(20)); 

        // List before reversal 
        Console.WriteLine("Given linked list:"); 
        list.PrintList(); 

        // Reverse the list 
        list.ReverseList(); 

        // List after reversal 
        Console.WriteLine("Reversed linked list:"); 
        list.PrintList(); 
    } 
} 

class LinkedList { 
    Node head; 

    public class Node { 
        public int data; 
        public Node next; 

        public Node(int d) 
        { 
            data = d; 
            next = null; 
        } 
    } 

    // function to add a new node at 
    // the end of the list 
    public void AddNode(Node node) 
    { 
        if (head == null) 
            head = node; 
        else { 
            Node temp = head; 
            while (temp.next != null) { 
                temp = temp.next; 
            } 
            temp.next = node; 
        } 
    } 

    // function to reverse the list 
    public void ReverseList() 
    { 
        Node prev = null, current = head, next = null; 
        while (current != null) { 
            next = current.next; 
            current.next = prev; 
            prev = current; 
            current = next; 
        } 
        head = prev; 
    } 

    // function to print the list data 
    public void PrintList() 
    { 
        Node current = head; 
        while (current != null) { 
            Console.Write(current.data + " "); 
            current = current.next; 
        } 
        Console.WriteLine(); 
    } 
}