矩阵快速幂优化递推式 例：斐波那契数列

矩阵快速幂 例：斐波那契数列

#include<cstdio>#include<algorithm>#include<cstring>#include<iostream>using namespace std;const int M = 1e9+7;struct Matrix {long long a[2][2];Matrix() {memset(a, 0, sizeof(a));}Matrix operator * (const Matrix y) {Matrix ans;for(int i = 0; i <= 1; i++)for(int j = 0; j <= 1; j++)for(int k = 0; k <= 1; k++)ans.a[i][j] += a[i][k]*y.a[k][j];for(int i = 0; i <= 1; i++)for(int j = 0; j <= 1; j++)ans.a[i][j] %= M;return ans;}void operator = (const Matrix b) {for(int i = 0; i <= 1; i++)for(int j = 0; j <= 1; j++)a[i][j] = b.a[i][j];}};int solve(long long x) {Matrix ans, trs;ans.a[0][0] = ans.a[1][1] = 1;trs.a[0][0] = trs.a[1][0] = trs.a[0][1] = 1;while(x) {if(x&1) ans = ans*trs;trs = trs*trs;x >>= 1;}return ans.a[0][0];}int main() {int n;scanf("%d", &n);cout << solve(n-1) << endl;return 0;}