in this code
main (){
int n ; cin >> n ;
double arr[n] ;
for(int i = 0 ; i < n ; i++)cin >>arr[i] ;
int cnt = 0;
for(int i = 0 ; i < n-1 ; i++)
for(int j = i +1 ; j < n ; j ++ )
{
double l = log10(arr[i]+arr[j])/log10(2);
int r = l ;
if(l-(double)r==0) cnt++ ;
}
cout<<cnt ;
}
when input is
4 7 3 2 1 it gives cnt = 1 because the the compiler of codeforces when arr[i] =7 and arr[j]=1 gives l=3 but r=2 ! (it dosent happen in other compilers)
even this similar code gives wa i think because of the same reason 147734731 thanks .
Don't use
==to compare doubles.i did this
if ( fabs(l - (double)d) < 1e-9 ) cnt++ ;but it stil gives the same answer , i think there is a problem in casting because the DOUBLE << log10(7+1)/log10(2) = 3 >> != the INT << log10(7+1)/log10(2) = 2>> so , what modification should i do ? thanks.Oh, are you trying to use
int r = lto getrto be the value oflrounded?Then I think your issue is that it always rounds down. If
l = 2.99999999999, thenr = 2. Floating point calculations introduce small errors like that, especially if you use log10 and division...Two additional remarks:
__builtin_popcount.Even after making a few changes, this still gives TLE Here
I basically took into account the precision errors that are commonly ignored when people use "double"
However, to solve it under given constraints, you can simply precompute the powers of 2 you want to attain :)
Like this