There has been less and less data structure problems in 2020. I think that it is inevitable because interesting data structure problems are hard to create. Still, I feel very sad about this. Let's share interesting data structure problems that you enjoyed in 2020!

For me, I especially love GP of Tokyo A, GP of Tokyo L and GP of Moscow D

I found the problems very cool! However, nobody is talking about it, so I decided to make a blog.

Tasks: https://boi2019.epy.gr/?p=747

Also, can someone post the scoreboard? I used to have a link http://147.102.38.13:8123/Ranking.html but the site died already...

How to do Roadtrip? It feels like doing a weird bfs storing a number of best paths in some form for each node, something like JOI Spring Camp 2017 Wild Boar

https://mirror.codeforces.com/contest/1185/submission/55779719

I'm getting ILE and i don't know why.

My code doesn't work on this test.

I tested it a lot of times and it works

LGMs and reds pls help :))

Problem source (Traditional Chinese): https://tioj.ck.tp.edu.tw/problems/2073

Basically, the problem asks to write a program to check whether the T<=5000 numbers (<=1e9) are prime. Moreover, your program must be in C++ and fits the following format:

#include <cstdio>

bool IsPrime(int n) {
  int r=1___f_____r__f___f____n___=0__%__f);
  return_____4_n__;
}

int main() {
  int x;
  while (~scanf("%d", &x)) printf("%d\n", (int)IsPrime(x));
}

You can edit each '_' with any character with ASCII code between 32 to 126.

I have tried to solve this problem for a long time and couldn't solve it. I have created a "solution", but it only works without -O2 optimization. Link: https://pastebin.com/K9sCXXn2

I desperately wanted to know the solution to this problem. Can somebody drop hints or solutions to this problem? Thanks!

I have seen a problem about bipartite matching on a special weighted graph and i would like to know the solution. The graph is similar to 875F - Royal Questions where nodes in one sides have at most 2 neighbours and the weight of these two edges are the same. However, each edge has 2 weights Ai and Bi, and the total weight is (sum of A)*(sum of B). The task is to find a maximum matching with highest total weight. N<=10000 and A,B<=30 where N is the number of nodes. Could someone give hints/solutions about this problem? Million thanks!

I recently participated on Codeforces Round 402 (Div. 1) and my code to problem A passed pretests with this.

http://mirror.codeforces.com/contest/778/submission/25032443

On line 31 there is this

"mid=(left+right)+1/2;"

My whole binary search is wrong but it still passed pretests

Should the pretest be set such that at least codes with this kind of mistakes shouldn't pass the pretests?