Who passed the "Course of Information Technology" in Yandex?

Question

Yandex

The contest is over, so I think we can announce the answers. I wonder what I fell asleep on.

Tell me at least how you counted non-zero bits in the file? For me, this was the most difficult question.

My solution, approximately, was this: Probably not very beautiful ... Another interesting thing about transferring a file between laptops.
od -An file | sed -e 's/7/111/g' -e 's/[356]/11/g' -e 's/[42]/1/g' | grep -o 1 | wc -l

Answer 1

Wrote govnokod on syah in response to non-zero bits.
But in fact, they later showed a solution based on hexdump - quite beautiful.
About the transmission - I answered something like this:
There are a lot of reasons, it is better to divide them into groups:
1) the cable is incorrectly crimped (just wrong or with a patch cord)
2) physical damage to the cable (broken cores, blablabla)
3) IP addresses from different subnets and other network setup problems
4) problems related to OS protection software (firewall, etc.)
5) nothing to transfer (smb/ftp/sftp servers not configured or something like that)
6) students are idiots (do not know how to transfer files)
Have taken.