Project Euler Problem 26

问题：

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.

答案：983
#include
#include


int main(void)
{
    int n, i, len, maxlen, maxn;
    maxlen = 0;
    for( n=2 ; n<=1000 ; n++ ){
        int rest = 1;
        int r0;
        for( i=0 ; i            rest = (rest*10)%n;
        r0 = rest;
        len = 0;
        do {
            rest = (rest*10)%n;
            len++;
        } while( rest!=r0 );
        if( len>maxlen ){
            maxn = n;
            maxlen = len;
        }
    }
    printf("The longest is %d\n", maxn);
    return 0;
}