How do I sort a file that has a very long list of items?

Question

I have a text file that has a very long list of items. So I want to sort them alphabetically but I do not want to load all the file into the memory (RAM).

I tried loading all the contents of the file to an array and sort them just like I do normally. But the system complains that there are no much memory!!

Thanks, Mohammad

Answer 1

You'll need to read up on external sorting. The basic approach is to use some sort of divide-and-conquer routine like merge sort, where you read and sort a portion of the file, then read and sort another portion of the file, etc. and when you get to the end you merge the sorted portions together.

Answer 2

Maybe the STXXL (Standard Template Library for Extra Large Data Sets) helps.

STXXL offers external sorting amongst others.