題意:求斐波那契數列的第n項,但是n很大,達到1e9
題解:由於n很大,所以不能逐項遞推,採用矩陣快速冪加速遞推,如圖
#include<cstdio>
#include<cstring>
#include<iostream>
#include<algorithm>
using namespace std;
const int MOD=1e4;
int n;
struct Matrix {
int v[2][2];
Matrix () {memset(v,0,sizeof(v));}
friend Matrix operator *(const Matrix &A,const Matrix &B) {
Matrix C;
for (int i=0;i<2;++i)
for (int j=0;j<2;++j)
for (int k=0;k<2;++k)
(C.v[i][j]+=A.v[i][k]*B.v[k][j]%MOD)%=MOD;
return C;
}
};
inline Matrix fpow(Matrix A,int m) {
Matrix R;
R.v[0][0]=R.v[1][1]=1;
while (m) {
if (m&1) R=A*R;
m>>=1,A=A*A;
}
return R;
}
int main() {
// freopen("in.txt","r",stdin);
Matrix A,B;
A.v[0][1]=A.v[1][0]=A.v[1][1]=1;
B.v[1][0]=1;
while (scanf("%d",&n)&&~n) {
if (n==0) {
puts("0");
continue;
}
Matrix M=fpow(A,n-1)*B;
printf("%d\n",M.v[1][0]);
}
return 0;
}