Add Merge Sort in Ruby

archive/r/ruby/merge-sort.rb

@@ -0,0 +1,50 @@
+# frozen_string_literal: true
+
+def usage!
+  abort %(Usage: please provide a list of at least two integers to sort in the format "1, 2, 3, 4, 5")
+end
+
+def parse_input
+  raw = ARGV.first
+  usage! if raw.nil? || raw.strip.empty?
+
+  numbers = raw.split(",").map { Integer(it.strip) }
+  usage! if numbers.length < 2
+
+  numbers
+rescue ArgumentError, NoMethodError
+  usage!
+end
+
+def merge_sort(arr)
+  return arr if arr.length <= 1
+
+  mid = arr.length / 2
+  left = merge_sort(arr[0...mid])
+  right = merge_sort(arr[mid..])
+
+  merge(left, right)
+end
+
+def merge(left, right)
+  i = 0
+  j = 0
+  result = []
+
+  while i < left.length && j < right.length
+    if left[i] <= right[j]
+      result << left[i]
+      i += 1
+    else
+      result << right[j]
+      j += 1
+    end
+  end
+
+  result.concat(left[i..] || [])
+  result.concat(right[j..] || [])
+  result
+end
+
+numbers = parse_input
+puts merge_sort(numbers).join(", ")