矩陣求斐波那契數列 -POJ 3070
In the Fibonacci integer sequence, F0 = 0, F1 = 1, and Fn = Fn − 1 + Fn − 2 for n ≥ 2. For example, the first ten terms of the Fibonacci sequence are:
0, 1, 1, 2, 3, 5, 8, 13, 21, 34, …
An alternative formula for the Fibonacci sequence is
.
Given an integer n, your goal is to compute the last 4 digits of Fn
Input
The input test file will contain multiple test cases. Each test case consists of a single line containing n (where 0 ≤ n ≤ 1,000,000,000). The end-of-file is denoted by a single line containing the number −1.
Output
For each test case, print the last four digits of Fn. If the last four digits of Fn
Sample Input
0 9 999999999 1000000000 -1
Sample Output
0 34 626 6875
Hint
As a reminder, matrix multiplication is associative, and the product of two 2 × 2 matrices is given by
.
Also, note that raising any 2 × 2 matrix to the 0th power gives the identity matrix:
.
如下圖:
#include<cstdio>
#include<cstring>
using namespace std;
struct node {
int m[3][3];
};
node a,e;
node mult(node a,node b) {
node c;
memset(c.m,0,sizeof(c.m));
for(int i=1; i<3; i++) {
for(int j=1; j<3; j++) {
for(int k=1; k<3; k++) {
c.m[i][j]+=(a.m[i][k]*b.m[k][j])%10000;
}
}
}
return c;
}
node cal(node a,int n) {
node res;
res = e;
while(n) {
if(n%2)
res = mult(a,res);
a = mult(a,a);
n=n/2;
}
return res;
}
int main() {
a.m[1][1]=1;
a.m[1][2]=1;
a.m[2][1]=1;
a.m[2][2]=0;
e.m[1][1]=1;
e.m[1][2]=0;
e.m[2][1]=0;
e.m[2][2]=1;
int n;
while(~scanf("%d",&n) && n>=0) {
node ans;
ans=cal(a,n);
printf("%d\n",ans.m[1][2]%10000);
}
return 0;
}