Hoj 1005 利用矩陣計算線性遞推式

#include <stdio.h>void matrix_mul(int (*a)[2],int (*b)[2]);//a = a * bvoid matrix_matrix(int n,int (*a)[2],int (*b)[2]);int main (){    int a,b,n,fn;    int f[2][2],ans[2][2];        while (1){    scanf("%d%d%d",&a,&b,&n);    if (a == 0 && b == 0 && n == 0 )    break;    f[0][0] = a;f[0][1] = 1;    f[1][0] = b;f[1][1] = 0;    ans[0][0] = 1;ans[0][1] = 0;    ans[1][0] = 0;ans[1][1] = 1;        matrix_matrix(n - 2,ans,f);    fn = (ans[0][0] + ans[1][0]) % 7 ;    printf("%d\n",fn);    }    return 0;}void matrix_mul(int (*a)[2],int (*b)[2]){        int i[2][2];        i[0][0] = (a[0][0] * b[0][0] + a[0][1] * b[1][0]) % 7;        i[0][1] = (a[0][0] * b[0][1] + a[0][1] * b[1][1]) % 7;        i[1][0] = (a[1][0] * b[0][0] + a[1][1] * b[1][0]) % 7;        i[1][1] = (a[1][0] * b[0][1] + a[1][1] * b[1][1]) % 7;        a[0][0] = i[0][0];a[1][0] = i[1][0];        a[0][1] = i[0][1];a[1][1] = i[1][1];        //printf("%d %d\n%d %d\n\n",a[0][0],a[0][1],a[1][0],a[1][1]);}void matrix_matrix(int n,int (*ans)[2],int (*f)[2]){    while (n != 0){        if (n % 2 == 1)    matrix_mul(ans,f);        n = n / 2;        matrix_mul(f,f);    }}