finding square root of a number in C++

Question

//find square root of a number n till d decimal points
#include<iostream>
#include<iomanip>

using namespace std;
int main(){
   int n;int d;cin>>n>>d;
   double x=n;int i=1;
   while(i<=20){
       float t=(x+n/x)/2;i++;x=t;
   }
   cout<<fixed<<setprecision(d)<<x<<endl;



   }

The algorithm seems correct,but when I think setprecision rounds off my number which I don't want. Any other alternative to setprecision() which doesn't round off my final answer? INPUT 10 4 gives me 3.1623 however answer is 3.1622 Also input 10 7 gives me 3.1622777 which does have a 2 on 4 th decimal place.

The point of precision is to determine when t round: here, 3.1623 is closer to 3.1622777 than 3.1622, so it's not wrong to round it to 3. A good example is pi, mostly used as 3.1416 while more precision gives 3.1415926535... both are just as correct, simply more precise — Adalcar
– Adalcar, Commented Dec 15, 2016 at 6:42
@Adalcar That's correct,but I still want answer as 3.1622, as answer is not getting passed by online judge — Harsh Pathak
– Harsh Pathak, Commented Dec 15, 2016 at 6:48

nishantsingh · Accepted Answer · 2016-12-15 06:53:15Z

2

To truncate the value to d decimal places, multiply with 10^d, take floor, and then divide by the same number.

double multiplier = pow(10, d);
double result = floor(t * multiplier) / multiplier;
cout << fixed << setprecision(d) << result << endl;

answered Dec 15, 2016 at 6:53

nishantsingh

4,6926 gold badges29 silver badges54 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Harsh Pathak Over a year ago

Thanks,but isn't there just a one statement function for giving my answer without rounding off?

nishantsingh Over a year ago

There might be. You'd have to search. This is the best I could come up with.

Collectives™ on Stack Overflow

finding square root of a number in C++

1 Answer 1

2 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related