洛谷P1962 斐波那契数列

#include <cstdio>
#include <algorithm>
#include <cstring>
#include <cctype>
using namespace std;
inline long long read() 
{
    long long x=0, f=1;
    char c;
    while (!isdigit(c=getchar())) 
    if (c == '-') f=-1;
    while(isdigit(c))
    x=(x<<3)+(x<<1)+(c&15),c=getchar();
    return x*f;
}
inline void write(long long x) 
{
    if(x<0)
    putchar('-'),write(~x+1);
    else{
        if(x > 9)
        write(x/10);
        putchar(x%10+'0');
    }
}
const int mod= 1000000007;
long long n;
struct matrix {
    long long mat[105][105];
    int n, m;
    matrix() 
    { 
        memset(mat,0,sizeof(mat)); 
        n=0;
        m=0; 
    }
    matrix(int val1,int val2) 
    { 
        memset(mat,0,sizeof(mat));
        n=val1;
        m=val2; 
    }
    matrix operator*(const matrix& rhs)const 
    {
        matrix ans(n,rhs.m);
        for (register int i=1; i<=n; i++)
            for (register int k=1;k<=m; k++)
                for (register int j=1; j<=rhs.m;j++)
                    ans.mat[i][j]=(ans.mat[i][j]+mat[i][k]*rhs.mat[k][j])%mod;
        return ans;
    }
    matrix operator*=(const matrix& rhs) 
    { 
        return *this=*this*rhs; 
    }
};
matrix power(matrix a, long long b) 
{
    matrix ans(1,2);
    ans.mat[1][1]=ans.mat[1][2]=1; 
    while(b) 
    {
        if (b&1)
        ans*=a;
        a*=a;
        b>>=1;
    }
    return ans;
}
int main() 
{
    n=read();
    if (n<=2) 
    {
       write(1);
       return 0;
    }
    matrix base(2,2);
    base.mat[1][1]=base.mat[1][2]=base.mat[2][1]=1;
    matrix ans=power(base,n-2);
    write(ans.mat[1][1]);
    return 0;
}