first?

qp

qp

When we are trying to submit a solution, there is no way to submit. Why?? And why the task is not readable? when we click in any problem, no descriptions is opened? Is it a bug or it could be a problem in my system?

hp

6

emm

The Problem G is exactly the same as the problem CodeChef Starters 121 / CHEFESCAPE. I used a silly BFS search when I solved it nearly 1.5 year ago, and this time I use a better and easier DSU to implement it.

Solution 1.5 year ago: here

Solution today: here

Problem $$$D$$$ is so annoying to implement.

For D, I tried to first separate the sequence into negative and positive part, then sort positives normally and sort negatives in reverse, then intersect them to restore the geometric sequence.

what could be the issue in the logic?

can't I just avoid floating point precision lost using big decimal?

Thanks for your amazing F, I really enjoy it

G too easy than other rounds' G. D too rubbish than other rounds' D.

Trash C.

F**KING AtCoder put a problem with ORIGIN IN PREVIOUS ABCs

Today's C

The origin

The exactly same code(modification is because of the different input format) can pass both problems.

Thank you for problems D and E, I submitted G, 3 mins late.

Hello

G is too easy for an ABC's G.

I took so long on D to find out that I forgot to check for r = +-1. Lost 20 mins to that and thus didn't have enough time to give to F. Oh well.

Problem G is basically a simple version of LC 3235.

noo i miss it

My stupid solution to problem F.

Main fact. Choose a cell. Look at answers for neighbouring cells. The first player will block the minimum one, so the second player will choose the second minimum one.

But we can't do it with a usual bfs, as the dependency is cyclic.

Idea 1. Process cells in increasing order of answer (like in Dijkstra). When the cell has at least two calculated neighbours, set the answer for it and insert it into set. This is fast and wrong, since we can miss the neighbour with less answer, which will be calculated later.

Idea 2. Do "for for" and calculate the answer for all cells as in idea 1. Do it again and again, until it stops change. This is correct and slow.

Idea 3. Do "Idea 1" ++ "Idea 2". This is AC.

Can anyone explain me in D, why abs(neg-pos)<=1 condition is there?

Problem D- Can anyone explain where my solution is wrong?

My Solution

I am sorting by absolute values and checking if $$$a_1, a_2, a_3$$$ be our sequence $$$a_2 \times a_2 = a_1 \times a_3$$$

#include <bits/stdc++.h>

using namespace std;
using ll = long long;

int gcd(int a, int b){
  if(abs(a)== 0){
    return abs(b);
  }
  return gcd(abs(b) % abs(a), abs(a));
}
int main(){
  ios::sync_with_stdio(0);
  cin.tie(0);
  freopen("input.txt", "r", stdin);
  int t; cin >> t;
  while(t--) {
    int n; cin >> n;
    vector <int> a(n);
    for(int i=0; i<n; i++){
      cin >> a[i];
    }
    sort(a.begin(), a.end(), [](int a, int b){
      if(abs(a) < abs(b)){
	return true;
      }
      return false;
    });
    if(n <= 2){
      cout << "Yes\n";
      continue;
    }
    int flag = 0;
    pair <int, int> r = {a[0]/gcd(a[0], a[1]), a[1]/gcd(a[0], a[1])};
    for(int i=1; i<n-1; i++){
      int fac = gcd(a[i], a[i+1]);
      if(((long long) r.second * (a[i]/fac) != (long long)r.first * (a[i+1]/ fac))){
	flag = 1;
	break;
      }
    }
    if(flag==0){
      cout << "Yes\n";
    }
    else {
      cout << "No\n";
    }
  }
}

Can anyone help me with what's wrong with this submission for problem : D submission Logic : 1) If the array contains only positive or only negative elements then just sort the array and check for GP. 2) If there are both positive and negative elements then again sort it , but this time look where to start the GP , for example consider the first positive element and first negative element , and u can decide based off whose magnitude is greater , then alternatively we can check for if its a GP as have done in the code.

Surprisingly , I got 29 WAs , wasnt expecting the logic to be soo wrong ...

Can anyone please help me in debugging my solution for problem D.

1)I sorted the array based on abs(value).

2)After that a general G.P check

3)And then if there is a mix of negative and positive elements then I tried checking if all the three elements are either +,-,+ or -,+,- .

Still I am getting only 3AC

https://atcoder.jp/contests/abc413/submissions/67371107

https://atcoder.jp/contests/abc413/submissions/67365983 why am i getting wrong ans can someone debug it

Problem C,why my code is wrong? https://atcoder.jp/contests/abc413/submissions/67412200

can anyone help me the with the approach of C?