After a busy weekend rowing abroad, it was finally time to get back to coding. By skipping one of my lectures on heaps, I managed to make it back home and join the contest only 20 minutes late, ready to solve some easy problems.

The contest went way worse than I expected — I only solved A and B. It might just be coping, but I think problems C and D were too difficult for Div. 4 — they felt Div. 3 level at the very least. I spent a good while trying to find some patterns on C, but couldn't manage to put together a solution. For problem D, I didn't notice very important key details and spent considerable time researching how to use bitsets, but even after I figured out how to read the bits of numbers, the solution I had didn't work and would probably have been too slow anyway. While doing problem E, I made a mistake when I came up with my algorithm to solve it, which turned out to be a major flaw that made the whole algorithm useless. It's a bit sad that I will most likely drop down below 1k, but I'll just climb back up.

I think that I'll do some problems on Leetcode involving bits to better prepare for questions like D. I'll also check out the editorials and try to find how I could come up with solutions for C and E once they get published.

'til the next contest!

same. mine was also an onsite contest so I panicked even more :(

I solve only 4 problems (A-D). It's not bad, but I wanted to solve all the problems or all except the last one (F in this contest). I think that last Div.3 and this Div.4 were difficult

C is a simple problem. Just pre calculate the answer for each possible value. D is a bit tricky, we need to observe one simple thing that a group can have at max 2 element when x ^ y = (1<<31-1) which is all ones. We can use two sum to solve this kind of problems.

two sum??

Two sum pattern. Sorry! You just need to find the pairs which can be clubbed together. By storing in a map.

ok thanks

i solved A,B,C. C was a pre-compute one. i gave the recent round 935 div3. and it was horrible experience. i solved 0 problems getting WA in A. will i get any rating change?