search for: caggatcatgctgcgcgcgnnnnnnnnnnnn

Hi, I want to group a large list (20 million) of strings into categories based on string similarity? The specific problem is: given a list of DNA sequence as below ACTCCCGCCGTTCGCGCGCAGCATGATCCTG ACTCCCGCCGTTCGCGCGCNNNNNNNNNNNN CAGGATCATGCTGCGCGCGAACGGCGGGAGT CAGGATCATGCTGCGCGCGAANNNNNNNNNN CAGGATCATGCTGCGCGCGNNNNNNNNNNNN ...... ..... NNNNNNNCCGTTCGCGCGCAGCATGATCCTG NNNNNNNNNNNNCGCGCGCAGCATGATCCTG NNNNNNNNNNNNGCGCGCGAACGGCGGGAGT NNNNNNNNNNNNNNCGCGCAGCATGATCCTG NNNNNNNNNNNTGCGCGCGAACGGCGGGAGT NNNNNNNNNNTTCGCGCGCAGCATGATCCTG 'N' is the missing letter It can be seen that some strings are the same except for t...