Merge pull request #125 from mingXta/linked-list

Add C# linkedlist doc and code,modify some formatting.

codes/csharp/.gitignore

@@ -0,0 +1,5 @@
+.idea/
+.vs/
+obj/
+.Debug
+bin/

codes/csharp/chapter_array_and_linkedlist/Array.cs

@@ -1,14 +1,16 @@
-/*
-* File: Array.cs
-* Created Time: 2022-12-14
-* Author: mingXta (1195669834@qq.com)
-*/
+// File: Array.cs
+// Created Time: 2022-12-14
+// Author: mingXta (1195669834@qq.com)
+
+using NUnit.Framework;
 
 namespace hello_algo.chapter_array_and_linkedlist
 {
     public class Array
     {
-        /* 随机返回一个数组元素 */
+        /// <summary>
+        /// 随机返回一个数组元素
+        /// </summary>
         public static int RandomAccess(int[] nums)
         {
             Random random = new();
@@ -17,7 +19,9 @@ namespace hello_algo.chapter_array_and_linkedlist
             return randomNum;
         }
 
-        /* 扩展数组长度 */
+        /// <summary>
+        /// 扩展数组长度
+        /// </summary>
         public static int[] Extend(int[] nums, int enlarge)
         {
             // 初始化一个扩展长度后的数组
@@ -31,7 +35,9 @@ namespace hello_algo.chapter_array_and_linkedlist
             return res;
         }
 
-        /* 在数组的索引 index 处插入元素 num */
+        /// <summary>
+        /// 在数组的索引 index 处插入元素 num
+        /// </summary>
         public static void Insert(int[] nums, int num, int index)
         {
             // 把索引 index 以及之后的所有元素向后移动一位
@@ -43,7 +49,9 @@ namespace hello_algo.chapter_array_and_linkedlist
             nums[index] = num;
         }
 
-        /* 删除索引 index 处元素 */
+        /// <summary>
+        /// 删除索引 index 处元素
+        /// </summary>
         public static void Remove(int[] nums, int index)
         {
             // 把索引 index 之后的所有元素向前移动一位
@@ -53,7 +61,9 @@ namespace hello_algo.chapter_array_and_linkedlist
             }
         }
 
-        /* 遍历数组 */
+        /// <summary>
+        /// 遍历数组
+        /// </summary>
         public static void Traverse(int[] nums)
         {
             int count = 0;
@@ -69,7 +79,9 @@ namespace hello_algo.chapter_array_and_linkedlist
             }
         }
 
-        /* 在数组中查找指定元素 */
+        /// <summary>
+        /// 在数组中查找指定元素
+        /// </summary>
         public static int Find(int[] nums, int target)
         {
             for (int i = 0; i < nums.Length; i++)
@@ -80,41 +92,44 @@ namespace hello_algo.chapter_array_and_linkedlist
             return -1;
         }
 
-        /*辅助函数,数组转字符串 */
+        /// <summary>
+        /// 辅助函数,数组转字符串
+        /// </summary>
         public static string ToString(int[] nums)
         {
             return string.Join(",", nums);
         }
         
-        /* Driver Code */
-        public static void Main()
+        // Driver Code 
+        [Test]
+        public static void Test()
         {
-            /* 初始化数组 */
+            // 初始化数组 
             int[] arr = new int[5];
             Console.WriteLine("数组 arr = " + ToString(arr));
             int[] nums = { 1, 3, 2, 5, 4 };
             Console.WriteLine("数组 nums = " + ToString(nums));
 
-            /* 随机访问 */
+            // 随机访问
             int randomNum = RandomAccess(nums);
             Console.WriteLine("在 nums 中获取随机元素 " + randomNum);
 
-            /* 长度扩展 */
+            // 长度扩展 
             nums = Extend(nums, 3);
             Console.WriteLine("将数组长度扩展至 8 ，得到 nums = " + ToString(nums));
 
-            /* 插入元素 */
+            // 插入元素 
             Insert(nums, 6, 3);
             Console.WriteLine("在索引 3 处插入数字 6 ，得到 nums = " + ToString(nums));
 
-            /* 删除元素 */
+            // 删除元素 
             Remove(nums, 2);
             Console.WriteLine("删除索引 2 处的元素，得到 nums = " + ToString(nums));
 
-            /* 遍历数组 */
+            // 遍历数组 
             Traverse(nums);
 
-            /* 查找元素 */
+            // 查找元素 
             int index = Find(nums, 3);
             Console.WriteLine("在 nums 中查找元素 3 ，得到索引 = " + index);
         }

codes/csharp/chapter_array_and_linkedlist/LinkedList.cs

@@ -0,0 +1,100 @@
+// File: LinkedList.cs
+// Created Time: 2022-12-16
+// Author: mingXta (1195669834@qq.com)
+
+using hello_algo.include;
+using NUnit.Framework;
+
+namespace hello_algo.chapter_array_and_linkedlist
+{
+    public class LinkedList
+    {
+        /// <summary>
+        /// 在链表的结点 n0 之后插入结点 P
+        /// </summary>
+        public static void Insert(ListNode n0, ListNode P)
+        {
+            ListNode n1 = n0.next;
+            n0.next = P;
+            P.next = n1;
+        }
+
+        /// <summary>
+        /// 删除链表的结点 n0 之后的首个结点
+        /// </summary>
+        public static void Remove(ListNode n0)
+        {
+            if (n0.next == null)
+                return;
+            // n0 -> P -> n1
+            ListNode P = n0.next;
+            ListNode n1 = P.next;
+            n0.next = n1;
+        }
+
+        /// <summary>
+        /// 访问链表中索引为 index 的结点
+        /// </summary>
+        public static ListNode Access(ListNode head, int index)
+        {
+            for (int i = 0; i < index; i++)
+            {
+                head = head.next;
+                if (head == null)
+                    return null;
+            }
+            return head;
+        }
+
+        /// <summary>
+        /// 在链表中查找值为 target 的首个结点
+        /// </summary>
+        public static int Find(ListNode head, int target)
+        {
+            int index = 0;
+            while (head != null)
+            {
+                if (head.val == target)
+                    return index;
+                head = head.next;
+                index++;
+            }
+            return -1;
+        }
+
+        // Driver Code 
+        [Test]
+        public void Test()
+        {
+            // 初始化链表 
+            // 初始化各个结点 
+            ListNode n0 = new ListNode(1);
+            ListNode n1 = new ListNode(3);
+            ListNode n2 = new ListNode(2);
+            ListNode n3 = new ListNode(5);
+            ListNode n4 = new ListNode(4);
+            // 构建引用指向
+            n0.next = n1;
+            n1.next = n2;
+            n2.next = n3;
+            n3.next = n4;
+            Console.WriteLine($"初始化的链表为{n0}");
+
+            // 插入结点 
+            Insert(n0, new ListNode(0));
+            Console.WriteLine($"插入结点后的链表为{n0}");
+
+            // 删除结点 
+            Remove(n0);
+            Console.WriteLine($"删除结点后的链表为{n0}");
+
+            // 访问结点 
+            ListNode node = Access(n0, 3);
+            Console.WriteLine($"链表中索引 3 处的结点的值 = {node.val}");
+
+            // 查找结点 
+            int index = Find(n0, 2);
+            Console.WriteLine($"链表中值为 2 的结点的索引 = {index}");    
+        }
+    }
+}

codes/csharp/hello-algo.csproj

@@ -0,0 +1,18 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net6.0</TargetFramework>
+    <RootNamespace>hello_algo</RootNamespace>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.4.0" />
+    <PackageReference Include="NUnit" Version="3.13.3" />
+	<PackageReference Include="NUnit3TestAdapter" Version="4.0.0" />
+	<PackageReference Include="coverlet.collector" Version="3.1.0" />
+  </ItemGroup>
+
+</Project>

codes/csharp/include/ListNode.cs

@@ -0,0 +1,68 @@
+// File: ListNode.cs
+// Created Time: 2022-12-16
+// Author: mingXta (1195669834@qq.com)
+
+namespace hello_algo.include
+{
+    /// <summary>
+    /// Definition for a singly-linked list node
+    /// </summary>
+    public class ListNode
+    {
+        public int val;
+        public ListNode next;
+
+        /// <summary>
+        /// Generate a linked list with an array
+        /// </summary>
+        /// <param name="x"></param>
+        public ListNode(int x)
+        {
+            val = x;
+        }
+
+        /// <summary>
+        /// Generate a linked list with an array
+        /// </summary>
+        /// <param name="arr"></param>
+        /// <returns></returns>
+        public static ListNode ArrToLinkedList(int[] arr)
+        {
+            ListNode dum = new ListNode(0);
+            ListNode head = dum;
+            foreach (int val in arr)
+            {
+                head.next = new ListNode(val);
+                head = head.next;
+            }
+            return dum.next;
+        }
+
+        /// <summary>
+        /// Get a list node with specific value from a linked list
+        /// </summary>
+        /// <param name="head"></param>
+        /// <param name="val"></param>
+        /// <returns></returns>
+        public static ListNode GetListNode(ListNode head, int val)
+        {
+            while (head != null && head.val != val)
+            {
+                head = head.next;
+            }
+            return head;
+        }
+
+        public override string? ToString()
+        {
+            List<string> list = new();
+            var head = this;
+            while (head != null)
+            {
+                list.Add(head.val.ToString());
+                head = head.next;
+            }
+            return string.Join("->", list);
+        }
+    }
+}

docs/chapter_array_and_linkedlist/linked_list.md

@@ -91,7 +91,13 @@ comments: true
 === "C#"
 
     ```csharp title=""
-
+    // 链表结点类
+    class ListNode
+    {
+        int val;         // 结点值
+        ListNode next;   // 指向下一结点的引用
+        ListNode(int x) => val = x;  //构造函数
+    }
     ```
 
 **尾结点指向什么？** 我们一般将链表的最后一个结点称为「尾结点」，其指向的是「空」，在 Java / C++ / Python 中分别记为 `null` / `nullptr` / `None` 。在不引起歧义下，本书都使用 `null` 来表示空。
@@ -202,7 +208,18 @@ comments: true
 === "C#"
 
     ```csharp title=""
-
+    // 初始化链表 1 -> 3 -> 2 -> 5 -> 4 
+    // 初始化各结点
+    n0 = new ListNode(1);
+    n1 = new ListNode(3);
+    n2 = new ListNode(2);
+    n3 = new ListNode(5);
+    n4 = new ListNode(4);
+    // 构建引用指向
+    n0.next = n1;
+    n1.next = n2;
+    n2.next = n3;
+    n3.next = n4;
     ```
 
 ## 链表优点
@@ -331,7 +348,24 @@ comments: true
 === "C#"
 
     ```csharp title=""
+    // 在链表的结点 n0 之后插入结点 P
+    void Insert(ListNode n0, ListNode P)
+    {
+        ListNode n1 = n0.next;
+        n0.next = P;
+        P.next = n1;
+    }
 
+    // 删除链表的结点 n0 之后的首个结点
+    void Remove(ListNode n0)
+    {
+        if (n0.next == null)
+            return;
+        // n0 -> P -> n1
+        ListNode P = n0.next;
+        ListNode n1 = P.next;
+        n0.next = n1;
+    }
     ```
 
 ## 链表缺点
@@ -422,7 +456,17 @@ comments: true
 === "C#"
 
     ```csharp title=""
-
+    // 访问链表中索引为 index 的结点
+    ListNode Access(ListNode head, int index)
+    {
+        for (int i = 0; i < index; i++)
+        {
+            head = head.next;
+            if (head == null)
+                return null;
+        }
+        return head;
+    }
     ```
 
 **链表的内存占用多。** 链表以结点为单位，每个结点除了保存值外，还需额外保存指针（引用）。这意味着同样数据量下，链表比数组需要占用更多内存空间。
@@ -526,7 +570,19 @@ comments: true
 === "C#"
 
     ```csharp title=""
-
+    // 在链表中查找值为 target 的首个结点
+    int Find(ListNode head, int target)
+    {
+        int index = 0;
+        while (head != null)
+        {
+            if (head.val == target)
+                return index;
+            head = head.next;
+            index++;
+        }
+        return -1;
+    }
     ```
 
 ## 常见链表类型
@@ -619,7 +675,13 @@ comments: true
 === "C#"
 
     ```csharp title=""
-
+    // 双向链表结点类 
+    class ListNode {
+        int val;        // 结点值
+        ListNode next;  // 指向后继结点的指针（引用）
+        ListNode prev;  // 指向前驱结点的指针（引用）
+        ListNode(int x) => val = x;  // 构造函数
+    }
     ```
 
 ![linkedlist_common_types](linked_list.assets/linkedlist_common_types.png)