Algorithm to merge files

[mutley]

Hi

I would like build some algorithm to join records of the textfile when the difference between two records is is less than 2

characteristics of records

1) The size is always 14 characters
2) The possible characters are: (1,2,3,4,5,6,7)
3) Usually has only the characters: 1.2 and / or 4

Should I read the file in sequential order, and find for each record all possible records that have difference of 1 or two characters
example of records
[pre]
42444442414411
42444441414211
42444441214411
42444421414411
42424441414411
42244441414411
41444442424411
41444442414421
41444442414412

[/pre]
When found some record less than 2 minimum difference, should add up the numbers that are different and eliminate one of the records
Example :
42444442414411 and 42444441414211

The two records merge into:42444443414611


As this record has already been summed, it is discarded in the next comparisons

What Is the best way to do It reading a text file ?