feat: add ruby code block - merge sort

codes/ruby/chapter_sorting/merge_sort.rb

@@ -0,0 +1,61 @@
+=begin
+File: merge_sort.rb
+Created Time: 2024-04-10
+Author: junminhong (junminhong1110@gmail.com)
+=end
+
+### 合并左子数组和右子数组 ###
+def merge(nums, left, mid, right)
+  # 左子数组区间为 [left, mid], 右子数组区间为 [mid+1, right]
+  # 创建一个临时数组tmp，用于存放合并后的结果
+  tmp = Array.new(right - left + 1)
+  # 初始化左子数组和右子数组的起始索引
+  i, j, k = left, mid + 1, 0
+  # 当左右子数组都还有元素时，进行比较并将较小的元素复制到临时数组中
+  while i <= mid and j <= right
+    if nums[i] <= nums[j]
+      tmp[k] = nums[i]
+      i += 1
+    else
+      tmp[k] = nums[j]
+      j += 1
+    end
+    k += 1
+  end
+  # 将左子数组和右子数组的剩余元素复制到临时数组中
+  while i <= mid
+    tmp[k] = nums[i]
+    i += 1
+    k += 1
+  end
+  while j <= right
+    tmp[k] = nums[j]
+    j += 1
+    k += 1
+  end
+  # 将临时数组tmp中的元素复制回原数组nums的对应区间
+  (0...tmp.length).each do |k|
+    nums[left + k] = tmp[k]
+  end
+end
+
+### 归并排序 ###
+def merge_sort(nums, left, right)
+  # 终止条件
+  # 当子数组长度为1时终止递归
+  return if left >= right
+  # 划分阶段
+  # 计算中点
+  mid = (left + right) / 2
+  # 递归左子数组
+  merge_sort(nums, left, mid)
+  # 递归右子数组
+  merge_sort(nums, mid + 1, right)
+  # 合并阶段
+  merge(nums, left, mid, right)
+end
+
+### Driver Code ###
+nums = [7, 3, 2, 6, 0, 1, 5, 4]
+merge_sort(nums, 0, nums.length - 1)
+puts "归并排序完成后 nums = #{nums.inspect}"