# [Haskell-cafe] Project Euler Problem 357 in Haskell

mukesh tiwari mukeshtiwari.iiitm at gmail.com
Tue Nov 8 13:46:27 CET 2011

```In that loop , I  am collecting all the primes in vector how ever I changed
the c++ code and  now it resembles to Haskell code. This code  still gives
the answer within a second.

#include<cstdio>
#include<iostream>
#include<vector>
#define Lim 100000001
using namespace std;

bool prime [Lim];
vector<int> v ;

void isPrime ()
{
for( int i = 2 ; i * i <= Lim ; i++)
if ( !prime [i]) for ( int j = i * i ; j <= Lim ; j += i ) prime
[j] = 1 ;

//for( int i = 2 ; i <= Lim ; i++) if ( ! prime[i] ) v.push_back( i
) ;
//cout<<v.size()<<endl;
//for(int i=0;i<10;i++) cout<<v[i]<<" ";cout<<endl;

}

int main()
{
isPrime();
int n = v.size();
long long sum = 0;
for(int i = 0 ; i < Lim ; i ++)
if ( ! prime [i])
{
int k = i-1;
bool f = 0;
for(int i = 1 ; i*i<= k ; i++)
if ( k % i == 0 && prime[ i + ( k / i ) ] )  { f=1 ; break
; }

if ( !f ) sum += k;
}
cout<<sum<<endl;
}

Regards
Mukesh Tiwari

On Tue, Nov 8, 2011 at 6:03 PM, Ivan Lazar Miljenovic <
ivan.miljenovic at gmail.com> wrote:

> On 8 November 2011 23:29, mukesh tiwari <mukeshtiwari.iiitm at gmail.com>
> wrote:
> >> Also, I'm not sure if the logic in the two versions is the same: I'm
> >> not sure about how you handle the boolean aspect in C++, but you have
> >> a third for-loop there that doesn't seem to correspond to anything in
> >> the Haskell version.
> >>
> > Which  loop ?
>
> for( int i = 2 ; i <= Lim ; i++) if ( ! prime[i] ) v.push_back( i ) ;
>
> --
> Ivan Lazar Miljenovic
> Ivan.Miljenovic at gmail.com
> IvanMiljenovic.wordpress.com
>
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```

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