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Lab 5: Crypt-analysis

If you are breaking a code, like an old school Caesar-cipher, then you'll want to know how common each letter is, how common each pair of letters is, and how common each triplet of letters is.

      
        lzrxogolnhbrxdoowrehfrphvxshusrzhuhg

The above letters make the phrase "I would like you all to become super powered" but where each letter is shifted forward by three in the alphabet.

Your Mission:

Write a function which consumes a string (likely containing encrypted plaintext) and produces two dictionaries:

A dictionary whose keys are the letters in the string and whose values are the frequencies of those letters (you'll find an example in class notes)
A dictionary whose keys are pairs of consecutive letters in the string and whose values are the frequencies of those pairs

Please ignore all whitespace and non-alphabetical characters.

An example:

If my function had the name ngram:

      
        ngram("banana man") ==
        ({"b":1, a":4, "n":3, "m":1},
        {"ba":1, "an":3, "na":2, "am":1, "ma":1})