feat: add ruby code block - merge sort

codes/ruby/chapter_sorting/merge_sort.rb

@@ -0,0 +1,60 @@
+=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, 0)
+ # 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 && 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
+ mid = (left + right) / 2 # 计算中点
+ merge_sort(nums, left, mid) # 递归左子数组
+ merge_sort(nums, mid + 1, right) # 递归右子数组
+ # 合并阶段
+ merge(nums, left, mid, right)
+end
+
+### Driver Code ###
+if __FILE__ == $0
+ 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}"
+end