Why is my solution 281599833 failing on case 5? What is the issue with my logic?

I am stuck on my solution to 277938667. It gets stuck on testcase 2 subcase 21 and since it is interactive I can neither debug it nor see the specific test case where it fails.

Here is my approach — I will first query the point (1,1) and find the distance of the closest mine to it. If the distance is 0 that's the location of the mine so I return. Else, all the possible cells where the mine can lie are along a diagonal of the rectangle. Now, I query the starting and ending points of the diagonals. Again if the distance is 0 I report them. Else, there are two possible cases — either both return the distance to the mine on the diagonal or one returns that mine and the other returns distance to a cell to the other mine. Now Here, I know the cells lying on the diagonal follow a certain pattern. I assume both of the distances I got while querying those points to be distances to a mine on the diagonal and calculate the coordinates of those cells accordingly. Now for the last query, I query about one of the cells I calculated. If the distance is 0 that is my answer. Else, the other one has to be my answer. I don't see anything wrong with the approach. Can someone help?

Can someone point out what's wrong with this solution 277417581? PS — I am neither good with trees nor with interactive problems. Had to submit it while reading the blog and learning from test cases. In the dry run it did pass for example 1 though but submitting it said "int 32 expected" while the problem clearly asked me to submit it after an ! mark. Also, if there is any flaw in the logic please point it out as well. My approach was I would take a as 1 and iterate it through all the values of b from 1 to n. Since it is a tree and not a graph, I believe every edge will be connected to either directly or through intermediate nodes. So if the query gives 1 I push back 1 and b else x and b because let's say the query gave x = 3, then 3 is connected to both 1 and 4 so we gotta pass both 1 3 and 3 4 but since I am iterating over all values of b, 1 3 should be there already so I just need to pass 3 4, am I on the right track?

In last Edu Div2 round 12000ish people solved 3 problems. Today's Div 2, 8000ish people solved 3. What has happened all of a sudden since last 2 contests? My rank is going extremely down even after improving earlier I used to get positive change even after solving 2 problems. I have seen profiles of people getting positive change in specialist range after solving 2 div 2s in a contest getting ranks under 3k. But since past 2 contests it seems impossible for even a pupil to get a positive change after solving 3. I solved 3 problems today but could only get 6460 rank at the end.

I have just started recursion and while most of the concepts were pretty easy for me to understand and apply, I am stuck with one particular one — the famous Subset problem of Leetcode where you have to return all possible subsets of a set. I have seen the solution, watched an explanation but still feel I don't truly understand it. Never been so much stuck with a problem before. Also, I don't think it is a problem that can be skipped because since the time I first saw it (last week) I have reduced 5 different problems to it including one in a contest (which I obviously couldn't implement even after figuring out the logic because I can't solve the subset problem). I have also reduced some CSES problems like Apple Divison to it, but again, unable to solve for the same reason. Could anyone suggest any resources for the same?

I am facing a problem of having two different entries of my college in the organization part. One is National Institute of Technology Durgapur which I have currently kept and the other is NIT Durgapur which is the same college but the names written in a short form. Now the problem is both these sections seem to have different rank lists of their own and both are of the students of my college and I can't simultaneously be in both of them. Is there a way to merge the two?