Problem: https://codeforces.com/contest/1620/problem/E

I was trying to apply some dsu-like logic in Problem E, when they asked for replacement of every $$$x$$$ with $$$y$$$ in the array, but it gave me WA on test 4.

The idea which I used during the contest:

from = replacement[x], to = replacement[y]
while(replacement[to] != to) to = replacement[to];
replacement[from] = to;

And, the idea which gave AC after the contest,

replacement[x] = replacement[y]

I know that the latter one is clever and more sleek, but why the former one fails? Can anyone please suggest a counter-case for it?

Except for these idea, the rest of code was exact same!

Submission 1 (with first logic): https://codeforces.com/contest/1620/submission/139872871
Submission 2 (with second logic): https://codeforces.com/contest/1620/submission/139872969

While reviewing some of my suspected users, I found submissions of Js1.

If we closely at this guy's previous contest submissions: https://codeforces.com/submissions/Js1

We can easily deduct the following points:

• He has changed his template 3 times (specially from B to C problem), in the 3 problems he solved,

• In one of his previous contest, all of his submissions were skipped,

• And all of his submissions were AC in one go, which clearly shows how desperate he was (like other cheaters).

It is near-to-impossible for MOSS to detect these kind of cheaters, so I request MikeMirzayanov to take some action (again as in that previous contest) over it. And also, needless to say, thanks for giving us such a great platform like Codeforces.

You da bestt!! <3