MY CODE
You told me what you wanted and I answered the call. I wrote them with gawk. Later, moved them to java awk extention.
Are you familiar with the java awk extention?
If your unfamiliar with it, here is the documentation link http://jawk.sourceforge.net/
In addition, there is another tool that will convert awk to java to meet your other requirement where you requested of me not use any external libraries to solve these problem.
By the way, I bet you wanted to see the regular-expressions of golang used, but you'll have to hire me for that. Plus, in my opinion, it is unethical to ask for them. My reason for claiming that is because other companies have asked me to code for them and asked for specifics on IBM Websphere security code. I did not comply with their requests.
I prefer awk and php over java when I am working for free or on a short on time frame.
I answer each question with:
gawk -F, -f dijkstra.awk exam.txt
or
java -jar jawk.jar -F, -f dijkstra.awk exam.txt
or again the entire awk script can be converted to java by way of tool for converting awk to java
The golang program steps down each directory.