From cb32c525e733fda89485a585a5691ccc6a60e32b Mon Sep 17 00:00:00 2001
From: khoaxuantu <68913255+khoaxuantu@users.noreply.github.com>
Date: Fri, 3 May 2024 18:46:42 +0700
Subject: [PATCH] feat: Add Ruby code - chapter "Sorting" (#1333)

* feat: add ruby code - chapter sorting

* Update radix_sort.rb

---------

Co-authored-by: Yudong Jin <krahets@163.com>
---
 codes/ruby/chapter_sorting/bubble_sort.rb    | 51 ++++++++++++++
 codes/ruby/chapter_sorting/counting_sort.rb  | 62 +++++++++++++++++
 codes/ruby/chapter_sorting/radix_sort.rb     | 70 ++++++++++++++++++++
 codes/ruby/chapter_sorting/selection_sort.rb | 29 ++++++++
 4 files changed, 212 insertions(+)
 create mode 100644 codes/ruby/chapter_sorting/bubble_sort.rb
 create mode 100644 codes/ruby/chapter_sorting/counting_sort.rb
 create mode 100644 codes/ruby/chapter_sorting/radix_sort.rb
 create mode 100644 codes/ruby/chapter_sorting/selection_sort.rb

diff --git a/codes/ruby/chapter_sorting/bubble_sort.rb b/codes/ruby/chapter_sorting/bubble_sort.rb
new file mode 100644
index 000000000..c97764267
--- /dev/null
+++ b/codes/ruby/chapter_sorting/bubble_sort.rb
@@ -0,0 +1,51 @@
+=begin
+File: bubble_sort.rb
+Created Time: 2024-05-02
+Author: Xuan Khoa Tu Nguyen (ngxktuzkai2000@gmail.com)
+=end
+
+### 冒泡排序 ###
+def bubble_sort(nums)
+  n = nums.length
+  # 外循环：未排序区间为 [0, i]
+  for i in (n - 1).downto(1)
+    # 内循环：将未排序区间 [0, i] 中的最大元素交换至该区间的最右端
+    for j in 0...i
+      if nums[j] > nums[j + 1]
+        # 交换 nums[j] 与 nums[j + 1]
+        nums[j], nums[j + 1] = nums[j + 1], nums[j]
+      end
+    end
+  end
+end
+
+### 冒泡排序（标志优化）###
+def bubble_sort_with_flag(nums)
+  n = nums.length
+  # 外循环：未排序区间为 [0, i]
+  for i in (n - 1).downto(1)
+    flag = false # 初始化标志位
+
+    # 内循环：将未排序区间 [0, i] 中的最大元素交换至该区间的最右端
+    for j in 0...i
+      if nums[j] > nums[j + 1]
+        # 交换 nums[j] 与 nums[j + 1]
+        nums[j], nums[j + 1] = nums[j + 1], nums[j]
+        flag = true # 记录交换元素
+      end
+    end
+
+    break unless flag # 此轮“冒泡”未交换任何元素，直接跳出
+  end
+end
+
+### Driver Code ###
+if __FILE__ == $0
+  nums = [4, 1, 3, 1, 5, 2]
+  bubble_sort(nums)
+  puts "冒泡排序完成后 nums = #{nums}"
+
+  nums1 = [4, 1, 3, 1, 5, 2]
+  bubble_sort_with_flag(nums1)
+  puts "冒泡排序完成后 nums = #{nums1}"
+end
diff --git a/codes/ruby/chapter_sorting/counting_sort.rb b/codes/ruby/chapter_sorting/counting_sort.rb
new file mode 100644
index 000000000..ca86944e4
--- /dev/null
+++ b/codes/ruby/chapter_sorting/counting_sort.rb
@@ -0,0 +1,62 @@
+=begin
+File: counting_sort.rb
+Created Time: 2024-05-02
+Author: Xuan Khoa Tu Nguyen (ngxktuzkai2000@gmail.com)
+=end
+
+### 计数排序 ###
+def counting_sort_naive(nums)
+  # 简单实现，无法用于排序对象
+  # 1. 统计数组最大元素 m
+  m = 0
+  nums.each { |num| m = [m, num].max }
+  # 2. 统计各数字的出现次数
+  # counter[num] 代表 num 的出现次数
+  counter = Array.new(m + 1, 0)
+  nums.each { |num| counter[num] += 1 }
+  # 3. 遍历 counter ，将各元素填入原数组 nums
+  i = 0
+  for num in 0...(m + 1)
+    (0...counter[num]).each do
+      nums[i] = num
+      i += 1
+    end
+  end
+end
+
+### 计数排序 ###
+def counting_sort(nums)
+  # 完整实现，可排序对象，并且是稳定排序
+  # 1. 统计数组最大元素 m
+  m = nums.max
+  # 2. 统计各数字的出现次数
+  # counter[num] 代表 num 的出现次数
+  counter = Array.new(m + 1, 0)
+  nums.each { |num| counter[num] += 1 }
+  # 3. 求 counter 的前缀和，将“出现次数”转换为“尾索引”
+  # 即 counter[num]-1 是 num 在 res 中最后一次出现的索引
+  (0...m).each { |i| counter[i + 1] += counter[i] }
+  # 4. 倒序遍历 nums, 将各元素填入结果数组 res
+  # 初始化数组 res 用于记录结果
+  n = nums.length
+  res = Array.new(n, 0)
+  (n - 1).downto(0).each do |i|
+    num = nums[i]
+    res[counter[num] - 1] = num # 将 num 放置到对应索引处
+    counter[num] -= 1 # 令前缀和自减 1 ，得到下次放置 num 的索引
+  end
+  # 使用结果数组 res 覆盖原数组 nums
+  (0...n).each { |i| nums[i] = res[i] }
+end
+
+### Driver Code ###
+if __FILE__ == $0
+  nums = [1, 0, 1, 2, 0, 4, 0, 2, 2, 4]
+
+  counting_sort_naive(nums)
+  puts "计数排序（无法排序对象）完成后 nums = #{nums}"
+
+  nums1 = [1, 0, 1, 2, 0, 4, 0, 2, 2, 4]
+  counting_sort(nums1)
+  puts "计数排序完成后 nums1 = #{nums1}"
+end
diff --git a/codes/ruby/chapter_sorting/radix_sort.rb b/codes/ruby/chapter_sorting/radix_sort.rb
new file mode 100644
index 000000000..d5611ee74
--- /dev/null
+++ b/codes/ruby/chapter_sorting/radix_sort.rb
@@ -0,0 +1,70 @@
+=begin
+File: radix_sort.rb
+Created Time: 2024-05-03
+Author: Xuan Khoa Tu Nguyen (ngxktuzkai2000@gmail.com)
+=end
+
+### 获取元素 num 的第 k 位，其中 exp = 10^(k-1) ###
+def digit(num, exp)
+  # 转入 exp 而非 k 可以避免在此重复执行昂贵的次方计算
+  (num / exp) % 10
+end
+
+### 计数排序（根据 nums 第 k 位排序）###
+def counting_sort_digit(nums, exp)
+  # 十进制的位范围为 0~9 ，因此需要长度为 10 的桶数组
+  counter = Array.new(10, 0)
+  n = nums.length
+  # 统计 0~9 各数字的出现次数
+  for i in 0...n
+    d = digit(nums[i], exp) # 获取 nums[i] 第 k 位，记为 d
+    counter[d] += 1 # 统计数字 d 的出现次数
+  end
+  # 求前缀和，将“出现个数”转换为“数组索引”
+  (1...10).each { |i| counter[i] += counter[i - 1] }
+  # 倒序遍历，根据桶内统计结果，将各元素填入 res
+  res = Array.new(n, 0)
+  for i in (n - 1).downto(0)
+    d = digit(nums[i], exp)
+    j = counter[d] - 1 # 获取 d 在数组中的索引 j
+    res[j] = nums[i] # 将当前元素填入索引 j
+    counter[d] -= 1 # 将 d 的数量减 1
+  end
+  # 使用结果覆盖原数组 nums
+  (0...n).each { |i| nums[i] = res[i] }
+end
+
+### 基数排序 ###
+def radix_sort(nums)
+  # 获取数组的最大元素，用于判断最大位数
+  m = nums.max
+  # 按照从低位到高位的顺序遍历
+  exp = 1
+  while exp <= m
+    # 对数组元素的第 k 位执行计数排序
+    # k = 1 -> exp = 1
+    # k = 2 -> exp = 10
+    # 即 exp = 10^(k-1)
+    counting_sort_digit(nums, exp)
+    exp *= 10
+  end
+end
+
+### Driver Code ###
+if __FILE__ == $0
+  # 基数排序
+  nums = [
+    10546151,
+    35663510,
+    42865989,
+    34862445,
+    81883077,
+    88906420,
+    72429244,
+    30524779,
+    82060337,
+    63832996,
+  ]
+  radix_sort(nums)
+  puts "基数排序完成后 nums = #{nums}"
+end
diff --git a/codes/ruby/chapter_sorting/selection_sort.rb b/codes/ruby/chapter_sorting/selection_sort.rb
new file mode 100644
index 000000000..79fe73eea
--- /dev/null
+++ b/codes/ruby/chapter_sorting/selection_sort.rb
@@ -0,0 +1,29 @@
+=begin
+File: selection_sort.rb
+Created Time: 2024-05-03
+Author: Xuan Khoa Tu Nguyen (ngxktuzkai2000@gmail.com)
+=end
+
+### 选择排序 ###
+def selection_sort(nums)
+  n = nums.length
+  # 外循环：未排序区间为 [i, n-1]
+  for i in 0...(n - 1)
+    # 内循环：找到未排序区间内的最小元素
+    k = i
+    for j in (i + 1)...n
+      if nums[j] < nums[k]
+        k = j # 记录最小元素的索引
+      end
+    end
+    # 将该最小元素与未排序区间的首个元素交换
+    nums[i], nums[k] = nums[k], nums[i]
+  end
+end
+
+### Driver Code ###
+if __FILE__ == $0
+  nums = [4, 1, 3, 1, 5, 2]
+  selection_sort(nums)
+  puts "选择排序完成后 nums = #{nums}"
+end