rishi_07's blog

By rishi_07, history, 4 years ago, In English

These are my codes for the problem Compression Algorithm of ACM ICPC 2018 online round.
I don't understand what is the problem with the first solution.
Note: The expected precision was 10^-6.
Image 1
Image 2

 
 
 
 
  • Vote: I like it
  • +7
  • Vote: I do not like it

»
4 years ago, # |
  Vote: I like it 0 Vote: I do not like it

Auto comment: topic has been updated by rishi_07 (previous revision, new revision, compare).

»
4 years ago, # |
Rev. 5   Vote: I like it +4 Vote: I do not like it

Well they say "Your answer will be considered correct if the absolute error is less than 10 - 6". With printf("%.6lf") there is possibility you will print something with error equal to 10 - 6 which is considered wrong.

  • »
    »
    4 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    Hi, please check the first image. There I used setprecision(10). Still WA. This is not only my case, check this discussion on codechef Link

»
4 years ago, # |
  Vote: I like it -20 Vote: I do not like it

I can explain why the setprecision code gives WA but I have no idea about the printf . setprecision includes the number of digits before the decimal point also . So setting it to 9 + 6 should work.

  • »
    »
    4 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    In this Link user swetankmodi claimed to have used setprecision(18) but still got WA.

    • »
      »
      »
      4 years ago, # ^ |
        Vote: I like it 0 Vote: I do not like it
      #include <bits/stdc++.h>
      using namespace std;
       
      int main(void)
      {
      	ios::sync_with_stdio(false); cin.tie(0);
      	int t; cin >> t;
      	while(t--)
      	{
      		long long int n, k; cin >> n >> k;
      		long double ans = 2.0 * ((k-1)*n + 1) / k;
      		cout << fixed << setprecision(16) << ans << endl;
      	}
      } 
      

      This gave us AC

    • »
      »
      »
      4 years ago, # ^ |
        Vote: I like it +7 Vote: I do not like it

      yes, but the solution posted by @bhishma uses long double but I used only double. Maybe that caused the issue?

  • »
    »
    4 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    You're wrong. From http://www.cplusplus.com/reference/iomanip/setprecision/
    "Sets the decimal precision to be used to format floating-point values on output operations". Beside we submitted with setprecision(8) and it got accepted.

    • »
      »
      »
      4 years ago, # ^ |
        Vote: I like it +3 Vote: I do not like it

      Actually my main language is Java so I might be wrong , but I have seen this issue in some old codeforces blog . In that case how can you explain this

»
4 years ago, # |
  Vote: I like it +65 Vote: I do not like it

There is a difference between cout<<fixed<<setprecision(10)<<x; and cout<<setprecision(10)<<x;

Example:

long double x=1000000000000.13232; cout<<fixed<<setprecision(10)<<x;

Output: 1000000000000.1323242188

long double x=1000000000000.13232; cout<<setprecision(10)<<x;

Output: 1e+12

If u dont use fixed and the number is reasonably large u might lose precision

»
7 weeks ago, # |
  Vote: I like it 0 Vote: I do not like it

Can anyone explain the solution of this problem ? I have tried it for long but haven't come up with anything significant.