Project Euler task 26

A unit fraction contains 1 in the numerator. The decimal representation of the unit fractions with denominators 2 to 10 are given:

1/2	=	0.5
1/3	=	0.(3)
1/4	=	0.25
1/5	=	0.2
1/6	=	0.1(6)
1/7	=	0.(142857)
1/8	=	0.125
1/9	=	0.(1)
1/10	=	0.1

Where 0.1(6) means 0.166666..., and has a 1-digit recurring cycle. It can be seen that ¹/₇ has a 6-digit recurring cycle.

Find the value of d 1000 for which ¹/_d contains the longest recurring cycle in its decimal fraction part.

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#include < iostream >

#include < vector >

using namespace std;

int cycle(int _n) {

unsigned long long int num = 10;

int arr[1000];

for (int i = 0; i < 1000; i++) {

int d = num / _n; // integer

int r = num % _n; // remainder

if (r == 0)

return 0;

arr[i] = r;

for (int j = 0; j < i; j++)

if (arr[j] == r)

return (i - j);

num = r * 10;

}

return 0;

}

int main() {

int iMax = 0;

int iMaxNum = 0;

for (int i = 1; i < 1000; i++) {

int iTemp = cycle(i);

if (iTemp > iMax) {

iMax = iTemp;

iMaxNum = i;

}

}

cout << iMaxNum << " " << iMax << endl;

return 0;

}