How to assign a class to posts through one or display a thumbnail from left to right through one post?

Question

WordPress

Actually, I can not understand how quickly and easily to implement such functionality automatically. The first thing that came to mind was to catch the id through js and, if it is possible to divide by 2, set the class, inside which there will be a float with the desired value.
I think there are easier solutions :) I just can't formulate the search query correctly...
Many thanks in advance!

Answer 1

nth-child css
Or in the article output loop, the counter i, and if i is even before we add one class, if not even, then another class

Answer 2

Different thumbnail sizes on homepage?
just divide by 2