http://projecteuler.net/problem=26 [Answer:983]

#include <iostream>
#include <algorithm>

using namespace std;

int main()
{
const int N = 1000;
int postion
;

int d = 0;
int longest = 0;
for ( int i = 2; i < N; ++i )
{
postion[1] = 0;
fill( postion+1, postion+i, 0 );

int remainder = 1;
for ( int pos = 1; ; ++pos )
{
remainder = remainder * 10 % i;

if ( remainder == 0 )
{
break;
}

if ( postion[remainder] != 0 )
{
int diff = pos - postion[remainder];
if ( diff > longest )
{
longest = diff;
d = i;
}
break;
}

postion[remainder] = pos;
}
}

cout << d << endl;
return 0;
}