My_CP_Library/Matrix Fibonacci at main · ngducmanh21/My_CP_Library · GitHub

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
#include<bits/stdc++.h>
using namespace std;

const int MOD = 1e9 + 7;

struct matrix
{
    long long x[2][2];
    matrix()
    {
        memset(x , 0 , sizeof(x));
    }

};

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.x[i][j] += a.x[i][k] * b.x[k][j] % MOD) % MOD;
            }
return c;
}

matrix Pow(const matrix& T , long long n)
{
    if(n == 0)
    {
        matrix I;
        for (int i = 0 ; i < 2 ; ++i)
        {
            I.x[i][i] = 1;
        }
        return I;
    }
    matrix tmp = Pow(T, n / 2);
    tmp = tmp * tmp;
    if(n & 1) tmp =  tmp * T;
    return tmp;
}

long long n;

main(){
   ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
   matrix a;
   cin >> n;
   if(n <= 1)
   {
       return cout << n,0;
   }
   matrix T;
   T.x[0][0] = T.x[0][1] = T.x[1][0] = 1;
   T = Pow(T, n - 1);
   matrix u;
   u.x[0][0] = 1;
   matrix ans = T * u;
   cout << ans.x[0][0];
}