Question

I am trying to write an algorithm to rearrange the letters in a string in order of frequency and then alphabetical order. For instance, “apple” becomes “aelpp”. “banana” becomes “bnnaaa”.

I know a variety of languages, but I am using Python for now to code it. This is what I have so far, but it does not work because there is no frequency sorting.

def order(word):
  word = word.lower()
  storage = [0] * 26
  for c in word:
    storage[ord(c) - 97] += 1
  newWord = []
  for l, c in enumerate(storage):
    for i in range(0, storage[l]):
      newWord.append(chr(l + 97))
  return ''.join(newWord)

Any advice on how to most efficiently implement this algorithm correctly?

Answer 1

Here is a (mostly) pythonic example of how to deal with this problem in python,
I hope the comments are sufficient to explain what is happening:

words = ["apples", "banannas", "oranges"]

def main():
    # our list of jumbled words
    jumbled = []
    for word in words:
        # dictionary of letter / frequency pairs.
        letters = {};
        # get letter frequency
        for letter in word:
            if letter in letters:
                letters[letter] += 1
            else:
                letters[letter] = 1
        # sort the letter / frequency pairs on descending frequency
        jumbled_word = sorted(letters.items(), key = lambda x: x[1],
                                                              reverse = True)
        # join the letters back together and add to our jumbled words
        jumbled.append(''.join([x[0] for x in jumbled_word]))
        letters = {}

    # print out the jumbled words in alphabetical order
    for x in sorted(jumbled):
        print x

if __name__=="__main__":
    main()

this implementation will keep capital letters capital.