Add Duplicate Character Counter in Ruby (#3962)

archive/r/ruby/duplicate-character-counter.rb

@@ -0,0 +1,17 @@
+# Duplicate Character Counter
+if ARGV.length == 0 || ARGV[0] == ''
+  puts 'Usage: please provide a string'
+else
+   hash_count_duplicate_letters = ARGV[0].each_char.with_object(Hash.new(0)) {|a, b| b[a]+=1}
+   counter_duplicate_letters = 0
+   hash_count_duplicate_letters.each do |key, value|
+    if value>1
+        puts "#{key}: #{value}"
+        counter_duplicate_letters += 1
+    end
+end
+    if counter_duplicate_letters == 0 
+        puts "No duplicate characters"
+    end 
+end
+# end