How to find common strings among two very large files?

Question

I have two very large files (and neither of them would fit in memory). Each file has one string (which doesn\'t have spaces in

Answer 1

Depending on how similar the entries within one file is, it might be possible to create a Trie (not tree) from it. Using this trie you can iterate the other file and check each entry if it is inside the trie.

When you have more than 2 files, iterate over one file and build a new trie from the matches. This way the last trie you have will contain all the matches that are contained in all files.