feat(csharp/hashing): add code and update docs to chapter hashing (#568)

* feat(csharp/hashing): add code and update docs to chapter hashing

* revert linked list to list

codes/csharp/chapter_hashing/built_in_hash.cs

@@ -0,0 +1,36 @@
+/**
+* File: built_in_hash.cs
+* Created Time: 2023-06-26
+* Author: hpstory (hpstory1024@163.com)
+*/
+
+namespace hello_algo.chapter_hashing; 
+
+public class built_in_hash {
+    [Test]
+    public void Test() {
+        int num = 3;
+        int hashNum = num.GetHashCode();
+        Console.WriteLine("整数 " + num + " 的哈希值为 " + hashNum);
+
+        bool bol = true;
+        int hashBol = bol.GetHashCode();
+        Console.WriteLine("布尔量 " + bol + " 的哈希值为 " + hashBol);
+
+        double dec = 3.14159;
+        int hashDec = dec.GetHashCode();
+        Console.WriteLine("小数 " + dec + " 的哈希值为 " + hashDec);
+
+        string str = "Hello 算法";
+        int hashStr = str.GetHashCode();
+        Console.WriteLine("字符串 " + str + " 的哈希值为 " + hashStr);
+
+        object[] arr = { 12836, "小哈" };
+        int hashTup = arr.GetHashCode();
+        Console.WriteLine("数组 [" + string.Join(", ", arr) + "] 的哈希值为 " + hashTup);
+
+        ListNode obj = new ListNode(0);
+        int hashObj = obj.GetHashCode();
+        Console.WriteLine("节点对象 " + obj + " 的哈希值为 " + hashObj);
+    }
+}

codes/csharp/chapter_hashing/hash_map_chaining.cs

@@ -0,0 +1,143 @@
+/**
+* File: hash_map_chaining.cs
+* Created Time: 2023-06-26
+* Author: hpstory (hpstory1024@163.com)
+*/
+
+namespace hello_algo.chapter_hashing;
+
+/* 链式地址哈希表 */
+class HashMapChaining {
+    int size; // 键值对数量
+    int capacity; // 哈希表容量
+    double loadThres; // 触发扩容的负载因子阈值
+    int extendRatio; // 扩容倍数
+    List<List<Pair>> buckets; // 桶数组
+
+    /* 构造方法 */
+    public HashMapChaining() {
+        size = 0;
+        capacity = 4;
+        loadThres = 2 / 3.0;
+        extendRatio = 2;
+        buckets = new List<List<Pair>>(capacity);
+        for (int i = 0; i < capacity; i++) {
+            buckets.Add(new List<Pair>());
+        }
+    }
+
+    /* 哈希函数 */
+    private int hashFunc(int key) {
+        return key % capacity;
+    }
+
+    /* 负载因子 */
+    private double loadFactor() {
+        return (double)size / capacity;
+    }
+
+    /* 查询操作 */
+    public string get(int key) {
+        int index = hashFunc(key);
+        // 遍历桶，若找到 key 则返回对应 val
+        foreach (Pair pair in buckets[index]) {
+            if (pair.key == key) {
+                return pair.val;
+            }
+        }
+        // 若未找到 key 则返回 null
+        return null;
+    }
+
+    /* 添加操作 */
+    public void put(int key, string val) {
+        // 当负载因子超过阈值时，执行扩容
+        if (loadFactor() > loadThres) {
+            extend();
+        }
+        int index = hashFunc(key);
+        // 遍历桶，若遇到指定 key ，则更新对应 val 并返回
+        foreach (Pair pair in buckets[index]) {
+            if (pair.key == key) {
+                pair.val = val;
+                return;
+            }
+        }
+        // 若无该 key ，则将键值对添加至尾部
+        buckets[index].Add(new Pair(key, val));
+        size++;
+    }
+
+    /* 删除操作 */
+    public void remove(int key) {
+        int index = hashFunc(key);
+        // 遍历桶，从中删除键值对
+        foreach (Pair pair in buckets[index].ToList()) { 
+            if (pair.key == key) {
+                buckets[index].Remove(pair);
+            }
+        }
+        size--;   
+    }
+
+    /* 扩容哈希表 */
+    private void extend() {
+        // 暂存原哈希表
+        List<List<Pair>> bucketsTmp = buckets;
+        // 初始化扩容后的新哈希表
+        capacity *= extendRatio;
+        buckets = new List<List<Pair>>(capacity);
+        for (int i = 0; i < capacity; i++) {
+            buckets.Add(new List<Pair>());
+        }
+        size = 0;
+        // 将键值对从原哈希表搬运至新哈希表
+        foreach (List<Pair> bucket in bucketsTmp) {
+            foreach (Pair pair in bucket) {
+                put(pair.key, pair.val);
+            }
+        }
+    }
+
+    /* 打印哈希表 */
+    public void print() {
+        foreach (List<Pair> bucket in buckets) {
+            List<string> res = new List<string>();
+            foreach (Pair pair in bucket) {
+                res.Add(pair.key + " -> " + pair.val);
+            }
+            foreach (string kv in res) {
+                Console.WriteLine(kv);
+            }
+        }
+    }
+}
+
+public class hash_map_chaining {
+    [Test]
+    public void Test() {
+        /* 初始化哈希表 */
+        HashMapChaining map = new HashMapChaining();
+
+        /* 添加操作 */
+        // 在哈希表中添加键值对 (key, value)
+        map.put(12836, "小哈");
+        map.put(15937, "小啰");
+        map.put(16750, "小算");
+        map.put(13276, "小法");
+        map.put(10583, "小鸭");
+        Console.WriteLine("\n添加完成后，哈希表为\nKey -> Value");
+        map.print();
+
+        /* 查询操作 */
+        // 向哈希表输入键 key ，得到值 value
+        string name = map.get(13276);
+        Console.WriteLine("\n输入学号 13276 ，查询到姓名 " + name);
+
+        /* 删除操作 */
+        // 在哈希表中删除键值对 (key, value)
+        map.remove(12836);
+        Console.WriteLine("\n删除 12836 后，哈希表为\nKey -> Value");
+        map.print();
+    }
+}

codes/csharp/chapter_hashing/hash_map_open_addressing.cs

@@ -0,0 +1,155 @@
+/**
+* File: hash_map_open_addressing.cs
+* Created Time: 2023-06-26
+* Author: hpstory (hpstory1024@163.com)
+*/
+
+namespace hello_algo.chapter_hashing;
+
+/* 开放寻址哈希表 */
+class HashMapOpenAddressing {
+    int size; // 键值对数量
+    int capacity; // 哈希表容量
+    double loadThres; // 触发扩容的负载因子阈值
+    int extendRatio; // 扩容倍数
+    Pair[] buckets; // 桶数组
+    Pair removed; // 删除标记
+
+    /* 构造方法 */
+    public HashMapOpenAddressing() {
+        size = 0;
+        capacity = 4;
+        loadThres = 2.0 / 3.0;
+        extendRatio = 2;
+        buckets = new Pair[capacity];
+        removed = new Pair(-1, "-1");
+    }
+
+    /* 哈希函数 */
+    private int hashFunc(int key) {
+        return key % capacity;
+    }
+
+    /* 负载因子 */
+    private double loadFactor() {
+        return (double)size / capacity;
+    }
+
+    /* 查询操作 */
+    public string get(int key) {
+        int index = hashFunc(key);
+        // 线性探测，从 index 开始向后遍历
+        for (int i = 0; i < capacity; i++) {
+            // 计算桶索引，越过尾部返回头部
+            int j = (index + i) % capacity;
+            // 若遇到空桶，说明无此 key ，则返回 null
+            if (buckets[j] == null)
+                return null;
+            // 若遇到指定 key ，则返回对应 val
+            if (buckets[j].key == key && buckets[j] != removed)
+                return buckets[j].val;
+        }
+        return null;
+    }
+
+    /* 添加操作 */
+    public void put(int key, string val) {
+        // 当负载因子超过阈值时，执行扩容
+        if (loadFactor() > loadThres) {
+            extend();
+        }
+        int index = hashFunc(key);
+        // 线性探测，从 index 开始向后遍历
+        for (int i = 0; i < capacity; i++) {
+            // 计算桶索引，越过尾部返回头部
+            int j = (index + i) % capacity;
+            // 若遇到空桶、或带有删除标记的桶，则将键值对放入该桶
+            if (buckets[j] == null || buckets[j] == removed) {
+                buckets[j] = new Pair(key, val);
+                size += 1;
+                return;
+            }
+            // 若遇到指定 key ，则更新对应 val
+            if (buckets[j].key == key) {
+                buckets[j].val = val;
+                return;
+            }
+        }
+    }
+
+    /* 删除操作 */
+    public void remove(int key) {
+        int index = hashFunc(key);
+        // 线性探测，从 index 开始向后遍历
+        for (int i = 0; i < capacity; i++) {
+            // 计算桶索引，越过尾部返回头部
+            int j = (index + i) % capacity;
+            // 若遇到空桶，说明无此 key ，则直接返回
+            if (buckets[j] == null) {
+                return;
+            }
+            // 若遇到指定 key ，则标记删除并返回
+            if (buckets[j].key == key) {
+                buckets[j] = removed;
+                size -= 1;
+                return;
+            }
+        }
+    }
+
+    /* 扩容哈希表 */
+    private void extend() {
+        // 暂存原哈希表
+        Pair[] bucketsTmp = buckets;
+        // 初始化扩容后的新哈希表
+        capacity *= extendRatio;
+        buckets = new Pair[capacity];
+        size = 0;
+        // 将键值对从原哈希表搬运至新哈希表
+        foreach (Pair pair in bucketsTmp) {
+            if (pair != null && pair != removed) {
+                put(pair.key, pair.val);
+            }
+        }
+    }
+
+    /* 打印哈希表 */
+    public void print() {
+        foreach (Pair pair in buckets) {
+            if (pair != null) {
+                Console.WriteLine(pair.key + " -> " + pair.val);
+            } else {
+                Console.WriteLine("null");
+            }
+        }
+    }
+}
+
+public class hash_map_open_addressing {
+    [Test]
+    public void Test() {
+        /* 初始化哈希表 */
+        HashMapOpenAddressing map = new HashMapOpenAddressing();
+
+        /* 添加操作 */
+        // 在哈希表中添加键值对 (key, value)
+        map.put(12836, "小哈");
+        map.put(15937, "小啰");
+        map.put(16750, "小算");
+        map.put(13276, "小法");
+        map.put(10583, "小鸭");
+        Console.WriteLine("\n添加完成后，哈希表为\nKey -> Value");
+        map.print();
+
+        /* 查询操作 */
+        // 向哈希表输入键 key ，得到值 value
+        string name = map.get(13276);
+        Console.WriteLine("\n输入学号 13276 ，查询到姓名 " + name);
+
+        /* 删除操作 */
+        // 在哈希表中删除键值对 (key, value)
+        map.remove(16750);
+        Console.WriteLine("\n删除 16750 后，哈希表为\nKey -> Value");
+        map.print();
+    }
+}

codes/csharp/chapter_hashing/simple_hash.cs

@@ -0,0 +1,66 @@
+/**
+* File: simple_hash.cs
+* Created Time: 2023-06-26
+* Author: hpstory (hpstory1024@163.com)
+*/
+
+namespace hello_algo.chapter_hashing; 
+
+public class simple_hash {
+    /* 加法哈希 */
+    public static int addHash(string key) {
+        long hash = 0;
+        const int MODULUS = 1000000007;
+        foreach (char c in key) {
+            hash = (hash + c) % MODULUS;
+        }
+        return (int)hash;
+    }
+
+    /* 乘法哈希 */
+    public static int mulHash(string key) {
+        long hash = 0;
+        const int MODULUS = 1000000007;
+        foreach (char c in key) {
+            hash = (31 * hash + c) % MODULUS;
+        }
+        return (int)hash;
+    }
+
+    /* 异或哈希 */
+    public static int xorHash(string key) {
+        int hash = 0;
+        const int MODULUS = 1000000007;
+        foreach (char c in key) {
+            hash ^= c;
+        }
+        return hash & MODULUS;
+    }
+
+    /* 旋转哈希 */
+    public static int rotHash(string key) {
+        long hash = 0;
+        const int MODULUS = 1000000007;
+        foreach (char c in key) {
+            hash = ((hash << 4) ^ (hash >> 28) ^ c) % MODULUS;
+        }
+        return (int)hash;
+    }
+
+    [Test]
+    public void Test() {
+        string key = "Hello 算法";
+
+        int hash = addHash(key);
+        Console.WriteLine("加法哈希值为 " + hash);
+
+        hash = mulHash(key);
+        Console.WriteLine("乘法哈希值为 " + hash);
+
+        hash = xorHash(key);
+        Console.WriteLine("异或哈希值为 " + hash);
+
+        hash = rotHash(key);
+        Console.WriteLine("旋转哈希值为 " + hash);
+    }
+}

docs/chapter_hashing/hash_algorithm.md

@@ -338,7 +338,29 @@ $$
 === "C#"
 
     ```csharp title="built_in_hash.cs"
+    int num = 3;
+    int hashNum = num.GetHashCode();
+    // 整数 3 的哈希值为 3;
+
+    bool bol = true;
+    int hashBol = bol.GetHashCode();
+    // 布尔量 true 的哈希值为 1;
+
+    double dec = 3.14159;
+    int hashDec = dec.GetHashCode();
+    // 小数 3.14159 的哈希值为 -1340954729;
 
+    string str = "Hello 算法";
+    int hashStr = str.GetHashCode();
+    // 字符串 Hello 算法 的哈希值为 -586107568;
+
+    object[] arr = { 12836, "小哈" };
+    int hashTup = arr.GetHashCode();
+    // 数组 [12836, 小哈] 的哈希值为 42931033;
+
+    ListNode obj = new ListNode(0);
+    int hashObj = obj.GetHashCode();
+    // 节点对象 0 的哈希值为 39053774;
     ```
 
 === "Swift"