Compiler specific and undefined by Standards, since the expression suffers from "sequence point" which happens when a variable is accessed and modified more than once in the same expression.
And next time onwards please search before you post !
Just like you search normally. Although sololearn search is still not great, but it's improving. Tags are important as sololearn search relies heavily on tags. That's why people are often asked to use correct tags. Many do not understand that arbitary tags skews the search result.
You can also use google search as
<search phrase> site:www.sololearn.com
You will get better results than sololearn results.