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Poj 3070 Fibonacci (矩阵快速幂)

2016-09-04 15:39 423 查看
题目链接:http://poj.org/problem?id=3070

Fibonacci

Time Limit: 1000MS Memory Limit: 65536K
Total Submissions: 13262 Accepted: 9430
Description

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 are all zeros, print ‘0’; otherwise, omit any leading zeros (i.e., print Fn mod 10000).

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:


.

Source

题目大意:求斐波拉契数列F(n) % 10000

解析:题中很明显的提示,用矩阵快速幂去求

代码如下:

#include<iostream>
#include<algorithm>
#include<map>
#include<stack>
#include<queue>
#include<set>
#include<string>
#include<cstdio>
#include<cstring
bfdd
>
#include<cctype>
#include<cmath>
#define N 1000009
using namespace std;
const int inf = 0x3f3f3f3f;
const int mod = 1e9 + 7;
const double eps = 1e-8;
const double pi = acos(-1.0);
typedef long long LL;
int q_mod(int b)
{
int i, j;
int a[2][2] = {1, 1, 1, 0};
int tm[2][2];
int ans[2][2] = {1, 0, 0, 1};
while(b)
{
if(b & 1)
{
for(i = 0; i < 2; i++)
for(j = 0; j < 2; j++)
tm[i][j] = ans[i][j];
memset(ans, 0, sizeof(ans));
for(i = 0; i < 2; i++)
{
for(j = 0; j < 2; j++)
{
for(int k = 0; k < 2; k++)
{
ans[i][j] = ans[i][j] + tm[i][k] * a[k][j];
ans[i][j] %= 10000;
}
}
}
}
for(i = 0; i < 2; i++)
for(j = 0; j < 2; j++)
tm[i][j] = a[i][j];

memset(a, 0, sizeof(a));
for(i = 0; i < 2; i++)
{
for(j = 0; j < 2; j++)
{
for(int k = 0; k < 2; k++)
{
a[i][j] = a[i][j] + tm[i][k] * tm[k][j];
a[i][j] %= 10000;
}
}
}
b >>= 1;
}
return ans[0][1];
}
int main()
{
int n;
while(scanf("%d", &n), n != -1)
{
printf("%d\n", q_mod(n));
}
return 0;
}
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