hdu1005

找规律。最多在 7 * 7 = 49内循环。

#include <stdio.h>int a, b, n, i, t, s[50];int main ( ) {    while ( scanf ( "%d%d%d", &a, &b, &n ) != EOF && ( a || b || n ) ) {        s[1] = s[2] = 1;        for ( i = 3; i <= 50; ++i ) {            s[i] = ( a * s[i - 1] + b * s[i - 2] ) % 7;                                     if ( s[i] == 1 && s[i - 1] == 1 ) break;        }        t = i - 2;        printf ( "%d\n", s[(n - 1) % t + 1] );    }}