Add Maximum Array Rotation in Ruby

archive/r/ruby/maximum-array-rotation.rb

@@ -0,0 +1,37 @@
+# frozen_string_literal: true
+
+USAGE = 'Usage: please provide a list of integers (e.g. "8, 3, 1, 2")'
+
+def usage!
+  warn USAGE
+  exit 1
+end
+
+def parse_list(str)
+  str.split(",").map { Integer(it.strip) }
+rescue ArgumentError, NoMethodError
+  usage!
+end
+
+def max_rotation_sum(arr)
+  n = arr.size
+  total_sum = arr.sum
+  current = arr.each_with_index.sum { |v, i| i * v }
+
+  max = current
+
+  (1...n).each do |i|
+    last = arr[n - i]
+    current += total_sum - n * last
+    max = current if current > max
+  end
+
+  max
+end
+
+raw = ARGV.first
+usage! if raw.nil? || raw.strip.empty?
+
+arr = parse_list(raw)
+
+puts max_rotation_sum(arr)