Ruby

Comprehensive Challenges

def most_common_character(str)
  # Write your code here
end


def most_common_character(str)
  count_hash = form_count_hash(str)
  most_common, most_common_count = count_hash.max_by{|_,v| v}
  chars_with_same_count = find_chars_with_same_count(
    count_hash.reject { |key, _| key == most_common },
    most_common_count
  )
  return most_common if chars_with_same_count.empty?
  (chars_with_same_count << most_common).sort.first
end

def form_count_hash(str)
  count_hash = Hash.new(0)
  str.downcase.each_char do |c|
    count_hash[c] += 1
  end
  count_hash
end

def find_chars_with_same_count(count_hash, most_common_count)
  count_hash.select{ |k,v| v == most_common_count }&.keys
end
