What is the algorithm of heuristics diff? Is it comparing longest-match?

    So, if i originally have
    x
    b
    n
    then adding x a n on top of it, it will become
    x
    a
    n
    x
    b
    n

How can i know that i add x-a-n? Basically, isn't it comparing x-b-n and detect it has changes on 'b' block, so the 'b' block become a-n-x-b?

Edit: My bad, didn't see this https://news.ycombinator.com/item?id=11915351. It has been explained there.