### maroonrk's blog

By maroonrk, history, 7 weeks ago,

We will hold AtCoder Regular Contest 167.

The point values will be 300-500-700-700-800-1200.

We are looking forward to your participation!

• +67

 » 7 weeks ago, # |   +13 Why is F given 1200 score...
 » 7 weeks ago, # |   +15 Wish I won't drop back to 1 Kyu.
 » 7 weeks ago, # |   0 emm...
 » 7 weeks ago, # |   0 Stuck at C for more than 45 minutes before trying D and realizing that it is pretty doable.
 » 7 weeks ago, # |   0 Is there any O(T) solution for E?
•  » » 7 weeks ago, # ^ |   +10 Oh I found such a submission. I only thought of solutions for S=2k,3k,3k+2, but there's a simple solution for S=2k+1.
•  » » 7 weeks ago, # ^ |   +10 In fact only one in-contest submission used extended gcd while the other 12 are $O(T)$
 » 7 weeks ago, # |   0 my last formula of my sol is similar to editorial >>why it give me wa on B my solution `long long a, b; cin>>a>>b; vectorphi; for(long long i = 2;i*i<=a;i++){ if(a%i==0){ long long cnt = 0; while(a%i==0) cnt++, a/=i; phi.push_back(b*cnt+1); } } if(a>1) phi.push_back(b+1); long long ans = 1; for(auto i:phi){ ans = ans * (i%md); ans%=md; } ans = ans * (b%md); ans%=md; ans = ans * fst_pow(2, md-2); ans%=md; cout<
•  » » 7 weeks ago, # ^ |   +10 Because ans may not be even before you divide by 2. Correct answer is floor(ans/2).
•  » » » 7 weeks ago, # ^ | ← Rev. 4 →   0 okay thanks>>I changed the mod to 2 * mod and divide by 2 in the last and did not use 2^mod-2
 » 7 weeks ago, # |   0 can anyone explain about this? It seems that there exict a O(1) solution of problem E. https://atcoder.jp/contests/arc167/submissions/46638239
 » 7 weeks ago, # |   +1 Can anyone get me clear on the concept behind B? i did not get the editorial
 » 7 weeks ago, # |   0 Can anyone please explain why is my submission getting TLE for some cases where as it is running under 2 ms for all other cases.I'm doing exactly what editorial says : B * product of (e_i * B + 1) for all powers of prime factors, finally dividing it by 2.
•  » » 7 weeks ago, # ^ |   +3 Overflow probably
•  » » » 7 weeks ago, # ^ |   0 Yes, indeed it is. for loop condition : j * j <= A got overflowed thus making it endless loop.Thanks a lot for the help!!
 » 7 weeks ago, # |   0 why my solution fails?: problem Bmy approach: we gonna factorize A and focus on one prime from the factorization: I need to know how mcuh p there is in the product of the divisors of a^b suppose a=p^k * .. so the number of this prime in the product is: (sum from 1 to k*b)* product of (ki +1) where ki is the power of the otehr primes sequencially.after that I just divide by k why this fails? : https://atcoder.jp/contests/arc167/submissions/46638531
•  » » 7 weeks ago, # ^ |   0 It's wrong. You don't divide by k, you multiple by B then divide by 2. You also have to make sure if the number is odd before dividing by 2. This is doable by checking if all the numbers you're multiplying are odd
 » 7 weeks ago, # |   +8 Can someone explain solution of problem C?
 » 7 weeks ago, # | ← Rev. 2 →   +15 I think problem E would be a good math problem, but I don't think it's a good CP problem. It's so tricky that you can find 4 people who's rating is under 1600 among 13 people who solve the problem during the contest:(
 » 7 weeks ago, # |   0 About Problem B :Can anyone tell me why I set the mod 998244353 the answer was WA,but when I changed it to 998244353*2 ,it was AC ?