be9931c8a1
* feat: add ruby code - chapter hashing * feat: add ruby code blocks - chapter hashing * fix: comments
148 lines
3.9 KiB
Ruby
148 lines
3.9 KiB
Ruby
=begin
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File: hash_map_open_addressing.rb
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Created Time: 2024-04-13
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Author: Xuan Khoa Tu Nguyen (ngxktuzkai2000@gmail.com)
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=end
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require_relative './array_hash_map'
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### 开放寻址哈希表 ###
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class HashMapOpenAddressing
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TOMBSTONE = Pair.new(-1, '-1') # 删除标记
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### 构造方法 ###
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def initialize
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@size = 0 # 键值对数量
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@capacity = 4 # 哈希表容量
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@load_thres = 2.0 / 3.0 # 触发扩容的负载因子阈值
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@extend_ratio = 2 # 扩容倍数
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@buckets = Array.new(@capacity) # 桶数组
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end
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### 哈希函数 ###
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def hash_func(key)
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key % @capacity
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end
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### 负载因子 ###
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def load_factor
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@size / @capacity
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end
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### 搜索 key 对应的桶索引 ###
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def find_bucket(key)
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index = hash_func(key)
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first_tombstone = -1
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# 线性探测，当遇到空桶时跳出
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while !@buckets[index].nil?
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# 若遇到 key ，返回对应的桶索引
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if @buckets[index].key == key
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# 若之前遇到了删除标记，则将键值对移动至该索引处
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if first_tombstone != -1
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@buckets[first_tombstone] = @buckets[index]
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@buckets[index] = TOMBSTONE
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return first_tombstone # 返回移动后的桶索引
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end
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return index # 返回桶索引
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end
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# 记录遇到的首个删除标记
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first_tombstone = index if first_tombstone == -1 && @buckets[index] == TOMBSTONE
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# 计算桶索引，越过尾部则返回头部
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index = (index + 1) % @capacity
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end
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# 若 key 不存在，则返回添加点的索引
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first_tombstone == -1 ? index : first_tombstone
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end
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### 查询操作 ###
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def get(key)
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# 搜索 key 对应的桶索引
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index = find_bucket(key)
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# 若找到键值对，则返回对应 val
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return @buckets[index].val unless [nil, TOMBSTONE].include?(@buckets[index])
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# 若键值对不存在，则返回 nil
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nil
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end
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### 添加操作 ###
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def put(key, val)
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# 当负载因子超过阈值时，执行扩容
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extend if load_factor > @load_thres
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# 搜索 key 对应的桶索引
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index = find_bucket(key)
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# 若找到键值对，则覆盖 val 开返回
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unless [nil, TOMBSTONE].include?(@buckets[index])
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@buckets[index].val = val
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return
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end
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# 若键值对不存在，则添加该键值对
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@buckets[index] = Pair.new(key, val)
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@size += 1
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end
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### 删除操作 ###
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def remove(key)
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# 搜索 key 对应的桶索引
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index = find_bucket(key)
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# 若找到键值对，则用删除标记覆盖它
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unless [nil, TOMBSTONE].include?(@buckets[index])
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@buckets[index] = TOMBSTONE
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@size -= 1
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end
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end
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### 扩容哈希表 ###
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def extend
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# 暂存原哈希表
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buckets_tmp = @buckets
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# 初始化扩容后的新哈希表
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@capacity *= @extend_ratio
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@buckets = Array.new(@capacity)
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@size = 0
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# 将键值对从原哈希表搬运至新哈希表
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for pair in buckets_tmp
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put(pair.key, pair.val) unless [nil, TOMBSTONE].include?(pair)
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end
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end
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### 打印哈希表 ###
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def print
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for pair in @buckets
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if pair.nil?
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puts "Nil"
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elsif pair == TOMBSTONE
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puts "TOMBSTONE"
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else
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puts "#{pair.key} -> #{pair.val}"
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end
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end
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end
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end
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### Driver Code ###
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if __FILE__ == $0
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# 初始化哈希表
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hashmap = HashMapOpenAddressing.new
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# 添加操作
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# 在哈希表中添加键值对 (key, val)
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hashmap.put(12836, "小哈")
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hashmap.put(15937, "小啰")
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hashmap.put(16750, "小算")
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hashmap.put(13276, "小法")
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hashmap.put(10583, "小鸭")
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puts "\n添加完成后，哈希表为\nKey -> Value"
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hashmap.print
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# 查询操作
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# 向哈希表中输入键 key ，得到值 val
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name = hashmap.get(13276)
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puts "\n输入学号 13276 ，查询到姓名 #{name}"
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# 删除操作
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# 在哈希表中删除键值对 (key, val)
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hashmap.remove(16750)
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puts "\n删除 16750 后，哈希表为\nKey -> Value"
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hashmap.print
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end
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