Steaks-Codeforces Gym Problem(ArabellaCPC2019) Doubt

help
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1

Question-Problem - H - Codeforces
My Solution-Codeforces
Problem-Getting Wrong Answer on test case 50.

My thinking-
I tried to find out logic for this problem by analyzing various cases of n and k and took out one observation from that for every n-k steaks it takes 5 minutes.

Can anyone help with this question?

2

logic is correct but i think you have not applied this condition :- if(time<10) time=10;
Your solution is not visible

1 Like
3

Ohh good observation, wasn’t able to think about it :slightly_smiling_face:
But, now it get’s wrong answer on test case 61. I think we are missing another thing also.

Here’s my code:
int main(){
int n,k;cin>>n>>k;
int cnt=0;
if(n%k==0) cnt=(n/k);
else cnt=(n/k)+1;
ll ans=cnt*5;
(ans>10)?(cout<<ans):(cout<<“10”);
return 0;

}

4 
int main()
{
    crap;
    int n,k;
    cin>>n>>k;
    ll p=0;
    while(n>0)
    {
        p+=5;
        n=n-k;
    }
    if(p<10) p=10;
    cout<<p<<endl;
}

This is the accepted solution. Division operator will give you wrong answer.

2 Likes
5

Your division should be like this:

# include <bits/stdc++.h>
using namespace std;
 
int main ()
{
    long long n, k;
    cin >> n >> k;
    cout << max(10ll, (n + k - 1) / k * 5) << endl;
    return 0;
}
2 Likes
6

Thanks bro, but any reason for that?

7

i have one doubt.
can you explain thinking about this (n + k - 1) / k ?

8

Tell you an identity:
\lceil\frac{n}{k} \rceil = \lfloor \frac{n + k - 1}{k} \rfloor

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9

Then i think this should work also :- ceil(n/k);

1 Like
10

Wow. That would help :slightly_smiling_face:
Thanks.

11

maybe not, I’ve always been cautious about floating-point numbers.

2 Likes
12

You’re very welcome.

1 Like
13

That’s why it is giving wrong answer by this way.
Can you provide any test case for which this would fail?

1 Like
14

I’m not sure, I always thought it depended on your luck.

2 Likes
15

oh , thank you for clearing it.

16

Can you explain me in the B problem
(Problem - B - Codeforces)
that how the second output is Kilani?

17

It’ easy to see.
If Kilani subtracts 2 for the first time, Ayoub can only subtract 1, so Kilani can win.

18

But k is given as 1 :confused:

19

Can he subtracts max(1, m - k)?

20

oh!
Got it…
that was really stupid of me
(will just go and drown in shame)