Feel free to share some of your best solved problems that you felt interesting to solve or taught you something new in range of 1800-2200.
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I liked this problem although it is kind of classical but good to solve https://mirror.codeforces.com/contest/1155/problem/D
certainly!
2036F - XORificator 3000. Easy to think of the approach until you realize
that you were using a wrong datatype and long long won't pass. Gotta use unsigned int 64 for this one. Just changed the data type to get it passed. This problem is 1900 because everyone would have tried long long and failed. I still didn't figure out why long long is wrong for this one because it gives WA even for lower values but after this I started using unit_64 for all bitmask problems and problems where negative numbers aren't in input. If you do figure out why long long is failing even for lower values do tell me too!
long long works , just use (1ll<<i) instead of (1<<i) i guess
Just submitted the editorial code replacing #define int unit64_t with #define int long long and it gave WA on 1. 293274046
Replace (1<<i) with (1ll<<i) and try
In this editorial solution it does not work i guess, because it is using the properties of unsigned for shifting (maybe because test case 1 is wrong even though no overflow), but you need not use unsigned integers just do normally and take care if the value goes negative somewhere
Can you elaborate a little more about those properties like what makes it different from long long? I thought the only difference between these two is the range of numbers they store.
True!
https://mirror.codeforces.com/problemset/problem/461/B
https://mirror.codeforces.com/problemset/problem/1916/D
Another classical but rarely used idea: 1155E - Guess the Root.
Certainly!
This one changed my life a few hours ago https://mirror.codeforces.com/contest/280/problem/C
the best problem I've seen? the one I set: 2031E - Penchick and Chloe's Trees
1844G - Tree Weights and 1770F - Koxia and Sequence. The coolest problems I have seen.
https://mirror.codeforces.com/problemset/problem/1497/C2 https://mirror.codeforces.com/problemset/problem/1527/C THESE ARE OF NUMBER THEORY
https://mirror.codeforces.com/problemset/problem/1971/G THIS ONE IS BITMASK
The most difficult to prove (solution/checker/etc) looks the best, so that would be e-olymp/3673, but they changed design so..
ask this to pienotpi as he is the best coder in India and he lives 4 rooms before your room