feat: Add ruby codes - chapter "Heap" (#1300)

* init heap Ruby

* feature: finish chapter heap for ruby

* fix delete heap.rb

* fix: Fix code style

* Update codes/ruby/chapter_heap/my_heap.rb

Co-authored-by: khoaxuantu <68913255+khoaxuantu@users.noreply.github.com>

* Update codes/ruby/chapter_heap/top_k.rb

Co-authored-by: khoaxuantu <68913255+khoaxuantu@users.noreply.github.com>

* fix: apply the suggested changes

* fix to_a

* Update my_heap.rb

---------

Co-authored-by: khoaxuantu <68913255+khoaxuantu@users.noreply.github.com>
Co-authored-by: Yudong Jin <krahets@163.com>

codes/ruby/chapter_heap/my_heap.rb

@@ -0,0 +1,147 @@
+=begin
+File: my_heap.rb
+Created Time: 2024-04-19
+Author: Blue Bean (lonnnnnnner@gmail.com)
+=end
+
+require_relative '../utils/print_util'
+
+### 大顶堆 ###
+class MaxHeap
+  attr_reader :max_heap
+
+  ### 构造方法，根据输入列表建堆 ###
+  def initialize(nums)
+    # 将列表元素原封不动添加进堆
+    @max_heap = nums
+    # 堆化除叶节点以外的其他所有节点
+    parent(size - 1).downto(0) do |i|
+      sift_down(i)
+    end
+  end
+
+  ### 获取左子节点的索引 ###
+  def left(i)
+    2 * i + 1
+  end
+
+  ### 获取右子节点的索引 ###
+  def right(i)
+    2 * i + 2
+  end
+
+  ### 获取父节点的索引 ###
+  def parent(i)
+    (i - 1) / 2     # 向下整除
+  end
+
+  ### 交换元素 ###
+  def swap(i, j)
+    @max_heap[i], @max_heap[j] = @max_heap[j], @max_heap[i]
+  end
+
+  ### 获取堆大小 ###
+  def size
+    @max_heap.length
+  end
+
+  ### 判断堆是否为空 ###
+  def is_empty?
+    size == 0
+  end
+
+  ### 访问堆顶元素 ###
+  def peek
+    @max_heap[0]
+  end
+
+  ### 元素入堆 ###
+  def push(val)
+    # 添加节点
+    @max_heap << val
+    # 从底至顶堆化
+    sift_up(size - 1)
+  end
+
+  ### 从节点 i 开始，从底至顶堆化 ###
+  def sift_up(i)
+    loop do
+      # 获取节点 i 的父节点
+      p = parent(i)
+      # 当“越过根节点”或“节点无须修复”时，结束堆化
+      break if p < 0 || @max_heap[i] <= @max_heap[p]
+      # 交换两节点
+      swap(i, p)
+      # 循环向上堆化
+      i = p
+    end
+  end
+
+  ### 元素出堆 ###
+  def pop
+    # 判空处理
+    raise IndexError, "堆为空" if is_empty?
+    # 交换根节点与最右叶节点（交换首元素与尾元素）
+    swap(0, size - 1)
+    # 删除节点
+    val = @max_heap.pop
+    # 从顶至底堆化
+    sift_down(0)
+    # 返回堆顶元素
+    val
+  end
+
+  ### 从节点 i 开始，从顶至底堆化 ###
+  def sift_down(i)
+    loop do
+      # 判断节点 i, l, r 中值最大的节点，记为 ma
+      l, r, ma = left(i), right(i), i
+      ma = l if l < size && @max_heap[l] > @max_heap[ma]
+      ma = r if r < size && @max_heap[r] > @max_heap[ma]
+
+      # 若节点 i 最大或索引 l, r 越界，则无须继续堆化，跳出
+      break if ma == i
+
+      # 交换两节点
+      swap(i, ma)
+      # 循环向下堆化
+      i = ma
+    end
+  end
+
+  ### 打印堆（二叉树）###
+  def __print__
+    print_heap(@max_heap)
+  end
+end
+
+### Driver Code ###
+if __FILE__ == $0
+  # 初始化大顶堆
+  max_heap = MaxHeap.new([9, 8, 6, 6, 7, 5, 2, 1, 4, 3, 6, 2])
+  puts "\n输入列表并建堆后"
+  max_heap.__print__
+
+  # 获取堆顶元素
+  peek = max_heap.peek
+  puts "\n堆顶元素为 #{peek}"
+
+  # 元素入堆
+  val = 7
+  max_heap.push(val)
+  puts "\n元素 #{val} 入堆后"
+  max_heap.__print__
+
+  # 堆顶元素出堆
+  peek = max_heap.pop
+  puts "\n堆顶元素 #{peek} 出堆后"
+  max_heap.__print__
+
+  # 获取堆大小
+  size = max_heap.size
+  puts "\n堆元素数量为 #{size}"
+
+  # 判断堆是否为空
+  is_empty = max_heap.is_empty?
+  puts "\n堆是否为空 #{is_empty}"
+end

codes/ruby/chapter_heap/top_k.rb

@@ -0,0 +1,64 @@
+=begin
+File: top_k.rb
+Created Time: 2024-04-19
+Author: Blue Bean (lonnnnnnner@gmail.com)
+=end
+
+require_relative "./my_heap"
+
+### 元素入堆 ###
+def push_min_heap(heap, val)
+  # 元素取反
+  heap.push(-val)
+end
+
+### 元素出堆 ###
+def pop_min_heap(heap)
+  # 元素取反
+  -heap.pop
+end
+
+### 访问堆顶元素 ###
+def peek_min_heap(heap)
+  # 元素取反
+  -heap.peek
+end
+
+### 取出堆中元素 ###
+def get_min_heap(heap)
+  # 将堆中所有元素取反
+  heap.max_heap.map { |x| -x }
+end
+
+### 基于堆查找数组中最大的 k 个元素 ###
+def top_k_heap(nums, k)
+  # 初始化小顶堆
+  # 请注意：我们将堆中所有元素取反，从而用大顶堆来模拟小顶堆
+  max_heap = MaxHeap.new([])
+
+  # 将数组的前 k 个元素入堆
+  for i in 0...k
+    push_min_heap(max_heap, nums[i])
+  end
+
+  # 从第 k+1 个元素开始，保持堆的长度为 k
+  for i in k...nums.length
+    # 若当前元素大于堆顶元素，则将堆顶元素出堆、当前元素入堆
+    if nums[i] > peek_min_heap(max_heap)
+      pop_min_heap(max_heap)
+      push_min_heap(max_heap, nums[i])
+    end
+  end
+
+  get_min_heap(max_heap)
+end
+
+### Driver Code ###
+if __FILE__ == $0
+  nums = [1, 7, 6, 3, 2]
+  k = 3
+
+  res = top_k_heap(nums, k)
+  puts "最大的 #{k} 个元素为"
+  print_heap(res)
+end

codes/ruby/utils/print_util.rb

@@ -4,6 +4,8 @@
 Author: Xuan Khoa Tu Nguyen (ngxktuzkai2000@gmail.com)
 =end
 
+require_relative "./tree_node"
+
 ### 打印矩阵 ###
 def print_matrix(mat)
   s = []
@@ -68,3 +70,11 @@ def print_tree(root, prev=nil, is_right=false)
 def print_hash_map(hmap)
   hmap.entries.each { |key, value| puts "#{key} -> #{value}" }
 end
+
+### 打印堆 ###
+def print_heap(heap)
+  puts "堆的数组表示：#{heap}"
+  puts "堆的树状表示："
+  root = arr_to_tree(heap)
+  print_tree(root)
+end