P1962 斐波那契数列 【矩阵快速幂】

 1 #include <bits/stdc++.h>
 2 
 3 using namespace std;
 4 #define ll long long
 5 #define Min(a,b) ((a)>(b)?(b):(a))
 6 #define Max(a,b) ((a)>(b)?(a):(b))
 7 const ll mod = 1000000007;
 8 
 9 struct Matrix
10 {
11     ll a[3][3];
12     Matrix() { memset(a, 0, sizeof(a)); }
13     Matrix operator*(const Matrix & b) const
14     {
15         Matrix res;
16         for(int i = 0; i < 2; i ++)
17         {
18             for(int j = 0; j < 2; j++)
19             {
20                 for(int k = 0; k < 2; k++)
21                 {
22                     res.a[i][j] = (res.a[i][j] + a[i][k] * b.a[k][j]) % mod;
23                 }
24             }
25         }
26         return res;
27     }
28 } ans, base;
29 
30 void Pow(ll b)
31 {
32     while(b)
33     {
34         if(b&1)
35         {
36             ans = ans * base;
37         }
38         base = base * base;
39         b >>= 1;
40     }
41 }
42 
43 void init()
44 {
45     base.a[0][0] = 0, base.a[0][1] = 1;
46     base.a[1][0] = 1, base.a[1][1] = 1;
47     ans.a[0][0] = 1, ans.a[0][1] = 1;
48 }
49 
50 int main()
51 {
52     
53     ll n;
54     while(std::cin>>n)
55     {
56         if(n > 2)
57         {
58             init();
59             Pow(n - 2);
60             std::cout << ans.a[0][1] << std::endl;
61         }
62         else
63         {
64             std::cout << "1" << std::endl;
65         }
66     }
67     return 0;
68 }