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  1. #include<bits/stdc++.h>
  2. using namespace std;
  3. int n;
  4. double t;
  5. #define err 0.0000001
  6. vector<pair<double,double> > seg;
  7. double co;
  8. bool ok(double ans)
  9. {
  10.     co=0.0;
  11.     for(int i=0; i<n; i++)
  12.     {
  13.         if((ans+seg[i].second)<=0) return false;
  14.         co+=(seg[i].first)/(ans+seg[i].second);
  15.     }
  16.  
  17.     if(abs(co-t)<=err) return true;
  18.     else return false;
  19.  
  20. }
  21. int main()
  22. {
  23.  
  24.     cin>>n>>t;
  25.     double x,y;
  26.     for(int i=0; i<n; i++)
  27.     {
  28.         cin>>x>>y;
  29.         seg.push_back(make_pair(x,y));
  30.     }
  31.     double low=-1000.0,hi=1000.0;
  32.     double mid=(hi+low)/2.0;
  33.  
  34.     while(!ok(mid))
  35.     {
  36.         // cout<<mid<<" "<<co<<endl;
  37.         if(abs(co-0)<=err)
  38.         {
  39.             low=mid;
  40.         }
  41.         else  if(co<t)
  42.         {
  43.             hi=mid;
  44.         }
  45.         else if(co>t)
  46.         {
  47.             low=mid;
  48.         }
  49.         mid=(hi+low)/2.0;
  50.     }
  51.     // ok(-0.408653377);
  52.     printf("%.6f\n",mid);
  53.  
  54. }
  55.  
Success #stdin #stdout 0s 16064KB
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stdin
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Standard input is empty
stdout
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0.000000
https://ideone.com/KXtSr3
language:
C++14 (gcc 8.3)
created:
7 years ago
visibility:
public

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