From e1216657729be1799eff25d06abff3ccc61697cf Mon Sep 17 00:00:00 2001
From: khoaxuantu <68913255+khoaxuantu@users.noreply.github.com>
Date: Sun, 7 Apr 2024 13:48:48 +0700
Subject: [PATCH] feat: add ruby code - chapter stack and queue (#1230)

---
 .../chapter_stack_and_queue/array_deque.rb    | 144 +++++++++++++++
 .../chapter_stack_and_queue/array_queue.rb    | 106 +++++++++++
 .../chapter_stack_and_queue/array_stack.rb    |  77 ++++++++
 codes/ruby/chapter_stack_and_queue/deque.rb   |  41 +++++
 .../linkedlist_deque.rb                       | 167 ++++++++++++++++++
 .../linkedlist_queue.rb                       | 100 +++++++++++
 .../linkedlist_stack.rb                       |  86 +++++++++
 codes/ruby/chapter_stack_and_queue/queue.rb   |  37 ++++
 codes/ruby/chapter_stack_and_queue/stack.rb   |  36 ++++
 9 files changed, 794 insertions(+)
 create mode 100644 codes/ruby/chapter_stack_and_queue/array_deque.rb
 create mode 100644 codes/ruby/chapter_stack_and_queue/array_queue.rb
 create mode 100644 codes/ruby/chapter_stack_and_queue/array_stack.rb
 create mode 100644 codes/ruby/chapter_stack_and_queue/deque.rb
 create mode 100644 codes/ruby/chapter_stack_and_queue/linkedlist_deque.rb
 create mode 100644 codes/ruby/chapter_stack_and_queue/linkedlist_queue.rb
 create mode 100644 codes/ruby/chapter_stack_and_queue/linkedlist_stack.rb
 create mode 100644 codes/ruby/chapter_stack_and_queue/queue.rb
 create mode 100644 codes/ruby/chapter_stack_and_queue/stack.rb

diff --git a/codes/ruby/chapter_stack_and_queue/array_deque.rb b/codes/ruby/chapter_stack_and_queue/array_deque.rb
new file mode 100644
index 000000000..ba4b78058
--- /dev/null
+++ b/codes/ruby/chapter_stack_and_queue/array_deque.rb
@@ -0,0 +1,144 @@
+=begin
+File: array_deque.rb
+Created Time: 2024-04-05
+Author: Xuan Khoa Tu Nguyen (ngxktuzkai2000@gmail.com)
+=end
+
+### 基于环形数组实现的双向队列 ###
+class ArrayDeque
+  ### 获取双向队列的长度 ###
+  attr_reader :size
+
+  ### 构造方法 ###
+  def initialize(capacity)
+    @nums = Array.new(capacity, 0)
+    @front = 0
+    @size = 0
+  end
+
+  ### 获取双向队列的容量 ###
+  def capacity
+    @nums.length
+  end
+
+  ### 判断双向队列是否为空 ###
+  def is_empty?
+    size.zero?
+  end
+
+  ### 队首入队 ###
+  def push_first(num)
+    if size == capacity
+      puts '双向队列已满'
+      return
+    end
+
+    # 队首指针向左移动一位
+    # 通过取余操作实现 front 越过数组头部后回到尾部
+    @front = index(@front - 1)
+    # 将 num 添加至队首
+    @nums[@front] = num
+    @size += 1
+  end
+
+  ### 队尾入队 ###
+  def push_last(num)
+    if size == capacity
+      puts '双向队列已满'
+      return
+    end
+
+    # 计算队尾指针，指向队尾索引 + 1
+    rear = index(@front + size)
+    # 将 num 添加至队尾
+    @nums[rear] = num
+    @size += 1
+  end
+
+  ### 队首出队 ###
+  def pop_first
+    num = peek_first
+    # 队首指针向后移动一位
+    @front = index(@front + 1)
+    @size -= 1
+    num
+  end
+
+  ### 队尾出队 ###
+  def pop_last
+    num = peek_last
+    @size -= 1
+    num
+  end
+
+  ### 访问队首元素 ###
+  def peek_first
+    raise IndexError, '双向队列为空' if is_empty?
+
+    @nums[@front]
+  end
+
+  ### 访问队尾元素 ###
+  def peek_last
+    raise IndexError, '双向队列为空' if is_empty?
+
+    # 计算尾元素索引
+    last = index(@front + size - 1)
+    @nums[last]
+  end
+
+  ### 返回数组用于打印 ###
+  def to_array
+    # 仅转换有效长度范围内的列表元素
+    res = []
+    for i in 0...size
+      res << @nums[index(@front + i)]
+    end
+    res
+  end
+
+  private
+
+  ### 计算环形数组索引 ###
+  def index(i)
+    # 通过取余操作实现数组首尾相连
+    # 当 i 越过数组尾部后，回到头部
+    # 当 i 越过数组头部后，回到尾部
+    (i + capacity) % capacity
+  end
+end
+
+### Driver Code ###
+
+# 初始化双向队列
+deque = ArrayDeque.new(10)
+deque.push_last(3)
+deque.push_last(2)
+deque.push_last(5)
+puts "双向队列 deque = #{deque.to_array}"
+
+# 访问元素
+peek_first = deque.peek_first
+puts "队首元素 peek_first = #{peek_first}"
+peek_last = deque.peek_last
+puts "队尾元素 peek_last = #{peek_last}"
+
+# 元素入队
+deque.push_last(4)
+puts "元素 4 队尾入队后 deque = #{deque.to_array}"
+deque.push_first(1)
+puts "元素 1 队尾入队后 deque = #{deque.to_array}"
+
+# 元素出队
+pop_last = deque.pop_last
+puts "队尾出队元素 = #{pop_last}，队尾出队后 deque = #{deque.to_array}"
+pop_first = deque.pop_first
+puts "队尾出队元素 = #{pop_first}，队尾出队后 deque = #{deque.to_array}"
+
+# 获取双向队列的长度
+size = deque.size
+puts "双向队列长度 size = #{size}"
+
+# 判断双向队列是否为空
+is_empty = deque.is_empty?
+puts "双向队列是否为空 = #{is_empty}"
diff --git a/codes/ruby/chapter_stack_and_queue/array_queue.rb b/codes/ruby/chapter_stack_and_queue/array_queue.rb
new file mode 100644
index 000000000..28ec1f010
--- /dev/null
+++ b/codes/ruby/chapter_stack_and_queue/array_queue.rb
@@ -0,0 +1,106 @@
+=begin
+File: array_queue.rb
+Created Time: 2024-04-05
+Author: Xuan Khoa Tu Nguyen (ngxktuzkai2000@gmail.com)
+=end
+
+### 基于环形数组实现的队列 ###
+class ArrayQueue
+  ### 获取队列的长度 ###
+  attr_reader :size
+
+  ### 构造方法 ###
+  def initialize(size)
+    @nums = Array.new(size, 0) # 用于存储队列元素的数组
+    @front = 0 # 队首指针，指向队首元素
+    @size = 0 # 队列长度
+  end
+
+  ### 获取队列的容量 ###
+  def capacity
+    @nums.length
+  end
+
+  ### 判断队列是否为空 ###
+  def is_empty?
+    size.zero?
+  end
+
+  ### 入队 ###
+  def push(num)
+    raise IndexError, '队列已满' if size == capacity
+
+    # 计算队尾指针，指向队尾索引 + 1
+    # 通过取余操作实现 rear 越过数组尾部后回到头部
+    rear = (@front + size) % capacity
+    # 将 num 添加至队尾
+    @nums[rear] = num
+    @size += 1
+  end
+
+  ### 出队 ###
+  def pop
+    num = peek
+    # 队首指针向后移动一位，若越过尾部，则返回到数组头部
+    @front = (@front + 1) % capacity
+    @size -= 1
+    num
+  end
+
+  ### 访问队首元素 ###
+  def peek
+    raise IndexError, '队列为空' if is_empty?
+
+    @nums[@front]
+  end
+
+  ### 返回列表用于打印 ###
+  def to_array
+    res = Array.new(size, 0)
+    j = @front
+
+    for i in 0...size
+      res[i] = @nums[j % capacity]
+      j += 1
+    end
+
+    res
+  end
+end
+
+### Driver Code ###
+
+# 初始化队列
+queue = ArrayQueue.new(10)
+
+# 元素入队
+queue.push(1)
+queue.push(3)
+queue.push(2)
+queue.push(5)
+queue.push(4)
+puts "队列 queue = #{queue.to_array}"
+
+# 访问队首元素
+peek = queue.peek
+puts "队首元素 peek = #{peek}"
+
+# 元素出队
+pop = queue.pop
+puts "出队元素 pop = #{pop}"
+puts "出队后 queue = #{queue.to_array}"
+
+# 获取队列的长度
+size = queue.size
+puts "队列长度 size = #{size}"
+
+# 判断队列是否为空
+is_empty = queue.is_empty?
+puts "队列是否为空 = #{is_empty}"
+
+# 测试环形数组
+for i in 0...10
+  queue.push(i)
+  queue.pop
+  puts "第 #{i} 轮入队 + 出队后 queue = #{queue.to_array}"
+end
diff --git a/codes/ruby/chapter_stack_and_queue/array_stack.rb b/codes/ruby/chapter_stack_and_queue/array_stack.rb
new file mode 100644
index 000000000..b580626ac
--- /dev/null
+++ b/codes/ruby/chapter_stack_and_queue/array_stack.rb
@@ -0,0 +1,77 @@
+=begin
+File: array_stack.rb
+Created Time: 2024-04-06
+Author: Xuan Khoa Tu Nguyen (ngxktuzkai2000@gmail.com)
+=end
+
+### 基于数组实现的栈 ###
+class ArrayStack
+  ### 构造方法 ###
+  def initialize
+    @stack = []
+  end
+
+  ### 获取栈的长度 ###
+  def size
+    @stack.length
+  end
+
+  ### 判断栈是否为空 ###
+  def is_empty?
+    @stack.empty?
+  end
+
+  ### 入栈 ###
+  def push(item)
+    @stack << item
+  end
+
+  ### 出栈 ###
+  def pop
+    raise IndexError, '栈为空' if is_empty?
+
+    @stack.pop
+  end
+
+  ### 访问栈顶元素 ###
+  def peek
+    raise IndexError, '栈为空' if is_empty?
+
+    @stack.last
+  end
+
+  ### 返回列表用于打印 ###
+  def to_array
+    @stack
+  end
+end
+
+### Driver Code ###
+
+# 初始化栈
+stack = ArrayStack.new
+
+# 元素入栈
+stack.push(1)
+stack.push(3)
+stack.push(2)
+stack.push(5)
+stack.push(4)
+puts "栈 stack = #{stack.to_array}"
+
+# 访问栈顶元素
+peek = stack.peek
+puts "栈顶元素 peek = #{peek}"
+
+# 元素出栈
+pop = stack.pop
+puts "出栈元素 pop = #{pop}"
+puts "出栈后 stack = #{stack.to_array}"
+
+# 获取栈的长度
+size = stack.size
+puts "栈的长度 size = #{size}"
+
+# 判断是否为空
+is_empty = stack.is_empty?
+puts "栈是否为空 = #{is_empty}"
diff --git a/codes/ruby/chapter_stack_and_queue/deque.rb b/codes/ruby/chapter_stack_and_queue/deque.rb
new file mode 100644
index 000000000..cef705e03
--- /dev/null
+++ b/codes/ruby/chapter_stack_and_queue/deque.rb
@@ -0,0 +1,41 @@
+=begin
+File: deque.rb
+Created Time: 2024-04-06
+Author: Xuan Khoa Tu Nguyen (ngxktuzkai2000@gmail.com)
+=end
+
+### Driver Code ###
+
+# 初始化双向队列
+# Ruby 没有内直的双端队列，只能把 Array 当作双端队列来使用
+deque = []
+
+# 元素如队
+deque << 2
+deque << 5
+deque << 4
+# 请注意，由于是数组，Array#unshift 方法的时间复杂度为 O(n)
+deque.unshift(3)
+deque.unshift(1)
+puts "双向队列 deque = #{deque}"
+
+# 访问元素
+peek_first = deque.first
+puts "队首元素 peek_first = #{peek_first}"
+peek_last = deque.last
+puts "队尾元素 peek_last = #{peek_last}"
+
+# 元素出队
+# 请注意，由于是数组， Array#shift 方法的时间复杂度为 O(n)
+pop_front = deque.shift
+puts "队首出队元素 pop_front = #{pop_front}，队首出队后 deque = #{deque}"
+pop_back = deque.pop
+puts "队尾出队元素 pop_back = #{pop_back}, 队尾出队后 deque = #{deque}"
+
+# 获取双向队列的长度
+size = deque.length
+puts "双向队列长度 size = #{size}"
+
+# 判断双向队列是否为空
+is_empty = size.zero?
+puts "双向队列是否为空 = #{is_empty}"
diff --git a/codes/ruby/chapter_stack_and_queue/linkedlist_deque.rb b/codes/ruby/chapter_stack_and_queue/linkedlist_deque.rb
new file mode 100644
index 000000000..0a9ae2e59
--- /dev/null
+++ b/codes/ruby/chapter_stack_and_queue/linkedlist_deque.rb
@@ -0,0 +1,167 @@
+=begin
+File: linkedlist_deque.rb
+Created Time: 2024-04-06
+Author: Xuan Khoa Tu Nguyen (ngxktuzkai2000@gmail.com)
+=end
+
+### 双向链表节点
+class ListNode
+  attr_accessor :val
+  attr_accessor :next # 后继节点引用
+  attr_accessor :prev # 前躯节点引用
+
+  ### 构造方法 ###
+  def initialize(val)
+    @val = val
+  end
+end
+
+### 基于双向链表实现的双向队列 ###
+class LinkedListDeque
+  ### 获取双向队列的长度 ###
+  attr_reader :size
+
+  ### 构造方法 ###
+  def initialize
+    @front = nil  # 头节点 front
+    @rear = nil   # 尾节点 rear
+    @size = 0     # 双向队列的长度
+  end
+
+  ### 判断双向队列是否为空 ###
+  def is_empty?
+    size.zero?
+  end
+
+  ### 入队操作 ###
+  def push(num, is_front)
+    node = ListNode.new(num)
+    # 若链表为空， 则令 front 和 rear 都指向 node
+    if is_empty?
+      @front = @rear = node
+    # 队首入队操作
+    elsif is_front
+      # 将 node 添加至链表头部
+      @front.prev = node
+      node.next = @front
+      @front = node # 更新头节点
+    # 队尾入队操作
+    else
+      # 将 node 添加至链表尾部
+      @rear.next = node
+      node.prev = @rear
+      @rear = node # 更新尾节点
+    end
+    @size += 1 # 更新队列长度
+  end
+
+  ### 队首入队 ###
+  def push_first(num)
+    push(num, true)
+  end
+
+  ### 队尾入队 ###
+  def push_last(num)
+    push(num, false)
+  end
+
+  ### 出队操作 ###
+  def pop(is_front)
+    raise IndexError, '双向队列为空' if is_empty?
+
+    # 队首出队操作
+    if is_front
+      val = @front.val # 暂存头节点值
+      # 删除头节点
+      fnext = @front.next
+      unless fnext.nil?
+        fnext.prev = nil
+        @front.next = nil
+      end
+      @front = fnext # 更新头节点
+    # 队尾出队操作
+    else
+      val = @rear.val # 暂存尾节点值
+      # 删除尾节点
+      rprev = @rear.prev
+      unless rprev.nil?
+        rprev.next = nil
+        @rear.prev = nil
+      end
+      @rear = rprev # 更新尾节点
+    end
+    @size -= 1 # 更新队列长度
+
+    val
+  end
+
+  ### 队首出队 ###
+  def pop_first
+    pop(true)
+  end
+
+  ### 队首出队 ###
+  def pop_last
+    pop(false)
+  end
+
+  ### 访问队首元素 ###
+  def peek_first
+    raise IndexError, '双向队列为空' if is_empty?
+
+    @front.val
+  end
+
+  ### 访问队尾元素 ###
+  def peek_last
+    raise IndexError, '双向队列为空' if is_empty?
+
+    @rear.val
+  end
+
+  ### 返回数组用于打印 ###
+  def to_array
+    node = @front
+    res = Array.new(size, 0)
+    for i in 0...size
+      res[i] = node.val
+      node = node.next
+    end
+    res
+  end
+end
+
+### Driver Code ###
+
+# 初始化双向队列
+deque = LinkedListDeque.new
+deque.push_last(3)
+deque.push_last(2)
+deque.push_last(5)
+puts "双向队列 deque = #{deque.to_array}"
+
+# 访问元素
+peek_first = deque.peek_first
+puts "队首元素 peek_first = #{peek_first}"
+peek_last = deque.peek_last
+puts "队首元素 peek_last = #{peek_last}"
+
+# 元素入队
+deque.push_last(4)
+puts "元素 4 队尾入队后 deque = #{deque.to_array}"
+deque.push_first(1)
+puts "元素 1 队首入队后 deque = #{deque.to_array}"
+
+# 元素出队
+pop_last = deque.pop_last
+puts "队尾出队元素 = #{pop_last}, 队尾出队后 deque = #{deque.to_array}"
+pop_first = deque.pop_first
+puts "队首出队元素 = #{pop_first}，队首出队后 deque = #{deque.to_array}"
+
+# 获取双向队列的长度
+size = deque.size
+puts "双向队列长度 size = #{size}"
+
+# 判断双向队列是否为空
+is_empty = deque.is_empty?
+puts "双向队列是否为空 = #{is_empty}"
diff --git a/codes/ruby/chapter_stack_and_queue/linkedlist_queue.rb b/codes/ruby/chapter_stack_and_queue/linkedlist_queue.rb
new file mode 100644
index 000000000..a21e94ab2
--- /dev/null
+++ b/codes/ruby/chapter_stack_and_queue/linkedlist_queue.rb
@@ -0,0 +1,100 @@
+=begin
+File: linkedlist_queue.rb
+Created Time: 2024-04-06
+Author: Xuan Khoa Tu Nguyen (ngxktuzkai2000@gmail.com)
+=end
+
+require_relative '../utils/list_node'
+
+### 基于链表头现的队列 ###
+class LinkedListQueue
+  ### 获取队列的长度 ###
+  attr_reader :size
+
+  ### 构造方法 ###
+  def initialize
+    @front = nil  # 头节点 front
+    @rear = nil   # 尾节点 rear
+    @size = 0
+  end
+
+  ### 判断队列是否为空 ###
+  def is_empty?
+    @front.nil?
+  end
+
+  ### 入队 ###
+  def push(num)
+    # 在尾节点后添加 num
+    node = ListNode.new(num)
+
+    # 如果队列为空，则令头，尾节点都指向该节点
+    if @front.nil?
+      @front = node
+      @rear = node
+    # 如果队列不为空，则令该节点添加到尾节点后
+    else
+      @rear.next = node
+      @rear = node
+    end
+
+    @size += 1
+  end
+
+  ### 出队 ###
+  def pop
+    num = peek
+    # 删除头节点
+    @front = @front.next
+    @size -= 1
+    num
+  end
+
+  ### 访问队首元素 ###
+  def peek
+    raise IndexError, '队列为空' if is_empty?
+
+    @front.val
+  end
+
+  ### 将链表为 Array 并返回 ###
+  def to_array
+    queue = []
+    temp = @front
+    while temp
+      queue << temp.val
+      temp = temp.next
+    end
+    queue
+  end
+end
+
+### Driver Code ###
+
+# 初始化队列
+queue = LinkedListQueue.new
+
+# 元素如队
+queue.push(1)
+queue.push(3)
+queue.push(2)
+queue.push(5)
+queue.push(4)
+puts "队列 queue = #{queue.to_array}"
+
+# 访问队首元素
+peek = queue.peek
+puts "队首元素 front = #{peek}"
+
+# 元素出队
+pop_front = queue.pop
+puts "出队元素 pop = #{pop_front}"
+puts "出队后 queue = #{queue.to_array}"
+
+# 获取队列的长度
+size = queue.size
+puts "队列长度 size = #{size}"
+
+# 判断队列是否为空
+is_empty = queue.is_empty?
+puts "队列是否为空 = #{is_empty}"
diff --git a/codes/ruby/chapter_stack_and_queue/linkedlist_stack.rb b/codes/ruby/chapter_stack_and_queue/linkedlist_stack.rb
new file mode 100644
index 000000000..36a04792e
--- /dev/null
+++ b/codes/ruby/chapter_stack_and_queue/linkedlist_stack.rb
@@ -0,0 +1,86 @@
+=begin
+File: linkedlist_stack.rb
+Created Time: 2024-04-06
+Author: Xuan Khoa Tu Nguyen (ngxktuzkai2000@gmail.com)
+=end
+
+require_relative '../utils/list_node'
+
+### 基于链表实现的栈 ###
+class LinkedListStack
+  attr_reader :size
+
+  ### 构造方法 ###
+  def initialize
+    @size = 0
+  end
+
+  ### 判断栈是否为空 ###
+  def is_empty?
+    @peek.nil?
+  end
+
+  ### 入栈 ###
+  def push(val)
+    node = ListNode.new(val)
+    node.next = @peek
+    @peek = node
+    @size += 1
+  end
+
+  ### 出栈 ###
+  def pop
+    num = peek
+    @peek = @peek.next
+    @size -= 1
+    num
+  end
+
+  ### 访问栈顶元素 ###
+  def peek
+    raise IndexError, '栈为空' if is_empty?
+
+    @peek.val
+  end
+
+  ### 将链表转化为 Array 并反回 ###
+  def to_array
+    arr = []
+    node = @peek
+    while node
+      arr << node.val
+      node = node.next
+    end
+    arr.reverse
+  end
+end
+
+### Driver Code ###
+
+# 初始化栈
+stack = LinkedListStack.new
+
+# 元素入栈
+stack.push(1)
+stack.push(3)
+stack.push(2)
+stack.push(5)
+stack.push(4)
+puts "栈 stack = #{stack.to_array}"
+
+# 访问栈顶元素
+peek = stack.peek
+puts "栈顶元素 peek = #{peek}"
+
+# 元素出栈
+pop = stack.pop
+puts "出栈元素 pop = #{pop}"
+puts "出栈后 stack = #{stack.to_array}"
+
+# 获取栈的长度
+size = stack.size
+puts "栈的长度 size = #{size}"
+
+# 判断是否为空
+is_empty = stack.is_empty?
+puts "栈是否为空 = #{is_empty}"
diff --git a/codes/ruby/chapter_stack_and_queue/queue.rb b/codes/ruby/chapter_stack_and_queue/queue.rb
new file mode 100644
index 000000000..cda1983a7
--- /dev/null
+++ b/codes/ruby/chapter_stack_and_queue/queue.rb
@@ -0,0 +1,37 @@
+=begin
+File: queue.rb
+Created Time: 2024-04-06
+Author: Xuan Khoa Tu Nguyen (ngxktuzkai2000@gmail.com)
+=end
+
+### Driver Code ###
+
+# 初始化队列
+# Ruby 内置的队列（Thread::Queue) 没有 peek 和遍历方法，可以把 Array 当作队列来使用
+queue = []
+
+# 元素入队
+queue.push(1)
+queue.push(3)
+queue.push(2)
+queue.push(5)
+queue.push(4)
+puts "队列 queue = #{queue}"
+
+# 访问队列元素
+peek = queue.first
+puts "队首元素 peek = #{peek}"
+
+# 元素出队
+# 清注意，由于是数组，Array#shift 方法时间复杂度为 O(n)
+pop = queue.shift
+puts "出队元素 pop = #{pop}"
+puts "出队后 queue = #{queue}"
+
+# 获取队列的长度
+size = queue.length
+puts "队列长度 size = #{size}"
+
+# 判断队列是否为空
+is_empty = queue.empty?
+puts "队列是否为空 = #{is_empty}"
diff --git a/codes/ruby/chapter_stack_and_queue/stack.rb b/codes/ruby/chapter_stack_and_queue/stack.rb
new file mode 100644
index 000000000..333ecf1d1
--- /dev/null
+++ b/codes/ruby/chapter_stack_and_queue/stack.rb
@@ -0,0 +1,36 @@
+=begin
+File: stack.rb
+Created Time: 2024-04-06
+Author: Xuan Khoa Tu Nguyen (ngxktuzkai2000@gmail.com)
+=end
+
+### Driver Code ###
+
+# 初始化栈
+# Ruby 没有内置的栈类，可以把 Array 当作栈来使用
+stack = []
+
+# 元素入栈
+stack << 1
+stack << 3
+stack << 2
+stack << 5
+stack << 4
+puts "栈 stack = #{stack}"
+
+# 访问栈顶元素
+peek = stack.last
+puts "栈顶元素 peek = #{peek}"
+
+# 元素出栈
+pop = stack.pop
+puts "出栈元素 pop = #{pop}"
+puts "出栈后 stack = #{stack}"
+
+# 获取栈的长度
+size = stack.length
+puts "栈的长度 size = #{size}"
+
+# 判断是否为空
+is_empty = stack.empty?
+puts "栈是否为空 = #{is_empty}"