feat: Add Ruby code - chapter "Hashing" (#1276)

* feat: add ruby code - chapter hashing

* feat: add ruby code blocks - chapter hashing

* fix: comments

codes/ruby/chapter_hashing/hash_map_chaining.rb

@@ -0,0 +1,128 @@
+=begin
+File: hash_map_chaining.rb
+Created Time: 2024-04-13
+Author: Xuan Khoa Tu Nguyen (ngxktuzkai2000@gmail.com)
+=end
+
+require_relative './array_hash_map'
+
+### 键式地址哈希表 ###
+class HashMapChaining
+  ### 构造方法 ###
+  def initialize
+    @size = 0 # 键值对数量
+    @capacity = 4 # 哈希表容量
+    @load_thres = 2.0 / 3.0 # 触发扩容的负载因子阈值
+    @extend_ratio = 2 # 扩容倍数
+    @buckets = Array.new(@capacity) { [] } # 桶数组
+  end
+
+  ### 哈希函数 ###
+  def hash_func(key)
+    key % @capacity
+  end
+
+  ### 负载因子 ###
+  def load_factor
+    @size / @capacity
+  end
+
+  ### 查询操作 ###
+  def get(key)
+    index = hash_func(key)
+    bucket = @buckets[index]
+    # 遍历桶，若找到 key ，则返回对应 val
+    for pair in bucket
+      return pair.val if pair.key == key
+    end
+    # 若未找到 key , 则返回 nil
+    nil
+  end
+
+  ### 添加操作 ###
+  def put(key, val)
+    # 当负载因子超过阈值时，执行扩容
+    extend if load_factor > @load_thres
+    index = hash_func(key)
+    bucket = @buckets[index]
+    # 遍历桶，若遇到指定 key ，则更新对应 val 并返回
+    for pair in bucket
+      if pair.key == key
+        pair.val = val
+        return
+      end
+    end
+    # 若无该 key ，则将键值对添加至尾部
+    pair = Pair.new(key, val)
+    bucket << pair
+    @size += 1
+  end
+
+  ### 删除操作 ###
+  def remove(key)
+    index = hash_func(key)
+    bucket = @buckets[index]
+    # 遍历桶，从中删除键值对
+    for pair in bucket
+      if pair.key == key
+        bucket.delete(pair)
+        @size -= 1
+        break
+      end
+    end
+  end
+
+  ### 扩容哈希表 ###
+  def extend
+    # 暫存原哈希表
+    buckets = @buckets
+    # 初始化扩容后的新哈希表
+    @capacity *= @extend_ratio
+    @buckets = Array.new(@capacity) { [] }
+    @size = 0
+    # 将键值对从原哈希表搬运至新哈希表
+    for bucket in buckets
+      for pair in bucket
+        put(pair.key, pair.val)
+      end
+    end
+  end
+
+  ### 打印哈希表 ###
+  def print
+    for bucket in @buckets
+      res = []
+      for pair in bucket
+        res << "#{pair.key} -> #{pair.val}"
+      end
+      pp res
+    end
+  end
+end
+
+### Driver Code ###
+if __FILE__ == $0
+  ### 初始化哈希表
+  hashmap = HashMapChaining.new
+
+  # 添加操作
+  # 在哈希表中添加键值对 (key, value)
+  hashmap.put(12836, "小哈")
+  hashmap.put(15937, "小啰")
+  hashmap.put(16750, "小算")
+  hashmap.put(13276, "小法")
+  hashmap.put(10583, "小鸭")
+  puts "\n添加完成后，哈希表为\n[Key1 -> Value1, Key2 -> Value2, ...]"
+  hashmap.print
+
+  # 查询操作
+  # 向哈希表中输入键 key ，得到值 value
+  name = hashmap.get(13276)
+  puts "\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)
+  hashmap.remove(12836)
+  puts "\n删除 12836 后，哈希表为\n[Key1 -> Value1, Key2 -> Value2, ...]"
+  hashmap.print
+end