编程之美-快速费波拉契数列

写出来也被它的速度吓了一跳，程序最坑的地方应该就是防止溢出了。

#include <stdio.h>
#include <stdlib.h>
#define MOD (19999997)
struct matrix
{
	unsigned long long a;
	unsigned long long b;        //{a,b}
	unsigned long long c;        //{c,d}
	unsigned long long d;
};
struct matrix mul_matrix(struct matrix a,struct matrix b) //return a*b
{
	struct matrix temp;
	temp.a=(a.a*b.a+a.b*b.c)%MOD;
	temp.b=(a.c*b.a+a.d*b.b)%MOD;
	temp.c=(a.a*b.b+a.b*b.d)%MOD;
	temp.d=(a.c*b.b+a.d*b.d)%MOD;
	return temp;
}
struct matrix pow_matrix(struct matrix ori)
{
	return mul_matrix(ori,ori);
}
int main(int argc, char*argv[])
{
    unsigned long max=atoi(argv[1]);
	struct matrix ms[32]; //pow(M,n)
	int i=1;
	ms[0].a=0;
	ms[0].b=1;
	ms[0].c=1;
	ms[0].d=1;
	for(i=1;i<32;i++) ms[i]=pow_matrix(ms[i-1]);

	struct matrix answer;
	answer.a=1;answer.b=0;answer.c=0;answer.d=1;// E matrix

	i=0;
	while(max)
	{
		if(max&0x01) answer=mul_matrix(answer,ms[i]);
		i++;
		max>>=1;
	}
	printf("%lld\n",(answer.d)%MOD);
	return 0;

}