How to find anagram frequency in a string?

Question

Given a string value of arbitrary length, you're supposed to determine the frequency of words which are anagrams of each other.

public static Map<String, Integer> generateAnagramFrequency(String str)
{ ... }

For example: if the string is "find art in a rat for cart and dna trac" your output should be a map: find -> 1 art -> 2 in -> 1 a -> 1 cart -> 2 and -> 2

The keys should be the first occurrence of the word, and the number is the number of anagrams of that word, including itself.

The solution i came up with so for is to sort all the words and compare each character from both strings till the end of either strings. It would be O(logn). I am looking for some other efficient method which doesn't change the 2 strings being compared. Thanks.

Answer 1

I've written a JavaScript implementation of creation a n-gram (word analysis), at Extract keyphrases from text (1-4 word ngrams).

This function can easily be altered to analyse the frequency of anagrams:
Replace s = text[i]; by s = text[i].sort(), so that the order of characters doesn't matter any more.

Answer 2

Create a "signature" for each word by sorting its letters alphabetically. Sort the words by their signatures. Run through the sorted list in order; if the signature is the same as the previous signature, you have an anagram.