Hello! Here is editorial!
Editorial
Code
Task B — Roman and lost numbers
Editorial
code
Editorial
Code
Editorial
Code
Task E — Roman and summer vacations
Editorial
Code
Task F — Roman and hard experiment
Editorial
Code
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Hello! Here is editorial!
I want to make some comments. long long should not work, but I forgot to make 10^18 after testing. I see many WA, because trunk(ans) returns double, you shold return int. Many people asked me about divide by zero. But in statements you can see, that answer exists. Task is simple if you are using Python or int128 on C++.
Task B — Roman and lost numbers
At first, s >= uneven num, because min uneven is 1 and uneven sum of should be not less than s. At second, s % 2 must be same as uneven sum % 2, because only uneven can change parity. That's all
You should see, that we answer requests in real time. For 1-st type we add name to set. For 2-nd type we check if the name is in set.
It is standart task. For sum you should use segment tree or prefix sums. For max we should build ST for max. Now we should print sum(l, r) — max(l, r)
Task E — Roman and summer vacations
All you should do is to find Pascal triangle. Now we find his tier: n = i + j — 2 and number: k = j — 1. Find answer as n! / k! / (n — k)! by module $$$10^9$$$ + 7. We take factorial by module dynamically
Task F — Roman and hard experiment
You should use mathematically expectation formule and no more. Here is explanations for it: a person turn right wuth probability $$$a[i]$$$, and go straight with probability $$$100-a[i]$$$ .
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I'm sorry if you can not understand sth. I want sleep:)
I think "parse" should be replaced by "editorial" everywhere, is it a mistranslation?
Yes
Done!
When clicking on your hyperlink to codes, it gives me
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E was good. I was doing n(n-1)(n-2)..../2*3*4..mod 1e9+7 but that was wrong solution. Btw, what's the intuition behind the formula for i+j-2 for finding the nth row?
Edit: nvm I wasn't dividing properly for the above formula to work. Thanks for the contest learned inverse mod division.
You 're welcome
A very good contest for beginners.
Thank u!