All source code file of solution is named in a "serialNum#problemName" or "serialNum#problem_name" format. For those who have intention to discuss about the solutions, this naming scheme would be convenient for referencing.
Now that different versions of same problem solved in one language were combined into one file. Multilingual solutions for one problem coexist.
The primary language of choice is Python. Others including C, golang, Java, Scala and even javascript. I find it useful to use LeetCode problems as a material to get familiar with a new language.