Square root of a 100 digit number in C++

Question

'unsigned long long' can solve upto 15 digits.

Is there a way to find square-root of a 100 digit number?

I know this is probably not what you're looking for, but in case you don't need an exact result, you can just use `double`. — Detheroc, Apr 14 '13 at 11:19
@Detheroc that would be a good first step to compute the real value with an algorithm like the newton method. — didierc, Apr 14 '13 at 11:51

awesoon · Answer 1 · 2013-04-14T12:59:02.487

You could also use Boost.Multiprecision library. This library provides wrappers for some popular multiprecision implementations.

#include <iostream>
#include <string>
#include <utility>

#include <boost/multiprecision/mpfr.hpp>

int main()
{
    std::string s(100, '0');
    s.at(0) = '1';
    boost::multiprecision::mpfr_float_100 f(std::move(s));
    boost::multiprecision::mpfr_float_100 sqrt = boost::multiprecision::sqrt(f);
    std::cout << sqrt.str() << std::endl;

    return 0;
}

score 3 · Answer 2 · answered Apr 14 '13 at 11:04

3

Definitely. One easy way would be to use the GNU multi-precision library's mpz_sqrt() function.

answered Apr 14 '13 at 11:04

John Zwinck

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score 3 · Answer 3 · answered Apr 14 '13 at 11:05

3

This question isnt really related to C++, but here is a list of methods you can use http://en.wikipedia.org/wiki/Methods_of_computing_square_roots

Depending on if its homework or not you might be able to use a premade lib to handle bignums

answered Apr 14 '13 at 11:05

krs

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Square root of a 100 digit number in C++

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