斐波那契數列的原理:
f(n) 是第n項的值;
f(1) = 1; f(2) = 1;
f(n) = f(n-1) + f(n-2);
故需求解那個2x2的矩陣即可,需用到二分法;
選擇二分法用遞歸求解:
#define N 2
using namespace std;
struct matrix{
int a[N][N];
};
matrix mul(matrix x,matrix y){
matrix ans;
ans.a[0][0] = x.a[0][0] * y.a[0][0] + x.a[0][1] * y.a[1][0];
ans.a[0][1] = x.a[0][0] * y.a[0][1] + x.a[0][1] * y.a[1][1];
ans.a[1][0] = x.a[1][0] * y.a[0][0] + x.a[1][1] * y.a[1][0];
ans.a[1][1] = x.a[1][0] * y.a[0][1] + x.a[1][1] * y.a[1][1];
x = ans;
return x;
}
matrix power(matrix x, long e){
matrix ans,tmp;
if(e == 0){
ans.a[0][0] = 1;
ans.a[0][1] = 0;
ans.a[1][0] = 0;
ans.a[1][1] = 1;
return ans;
}
if(e == 1)
return x;
tmp = power(x,e >>1);
ans = mul(tmp,tmp);
if(e & 1)
ans = mul(ans,x);
return ans;
}