- I fell into a very interesting situation today , while solving CF — 599D.
- say long long a = 1000000000000000363,b= 91
- I wrote long long c = ceil(a*1.0/b) thinking (long * double) / double should be perfect double and ceil(double) — should work out.
- I was expecting correct answer, c = 10989010989010993, but it produced c= 10989010989010994 , 1 more than the actual — result!!!! Damn to the precision issue.
- Option 1 : Study lot lot and lot about your compiler and how it manages precision while both implicit and explicit cast.
- Option 2 : Use your own ceil function like this
- template inline T ceil(T numerator ,T denominator)
- return (numerator+denominator-1)/denominator;
Moral : Avoid fraction as much as you can.