[Ruby] exercise _ Frequent Letters (복습할 것)

Write a method frequent_letters that takes in a string and returns an array containing the characters that appeared more than twice in the string.

 

def frequent_letters(string)

end

print frequent_letters('mississippi') #=> ["i", "s"]
puts
print frequent_letters('bootcamp') #=> []
puts

def frequent_letters(string)
  twice = []
  count = Hash.new(0)
  
  string.each_char do |char|
  	count[char] += 1
  end
  
  count.each do |char, num|
    if num > 2
      twice << char
    end
  end
  
  return twice

end

print frequent_letters('mississippi') #=> ["i", "s"]
puts
print frequent_letters('bootcamp') #=> []
puts

def frequent_letters(string)
  count = Hash.new(0)
  string.each_char { |char| count[char] += 1 }

  frequents = []
  count.each do |char, num|
    if num > 2
      frequents << char
    end
  end
  return frequents
end

print frequent_letters('mississippi') #=> ["i", "s"]
puts
print frequent_letters('bootcamp') #=> []
puts