| Time Limit: 1000MS | Memory Limit: 65536K | |
| Total Submissions: 5039 | Accepted: 3479 |
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:
.
题目大意就是求出斐波那契数列第k项的后四位,如果有前导0就不输出0,但最后一个0必须输出
刚开始的时候就想到了一个关于斐波那契数列的数列的一个公式,准备用那个公式求的,但题目已经提示了用矩阵,就没用那个公式
有兴趣的可以看看这个公式,试试能不能那个解这题

这一题就要注意到矩阵
的右上角或左下角对应的值正好是第n项的值
故可以通过快速幂来求得斐波那契数列的哦n项,由于数据较大,还要记得要不断的对10000取模
矩阵的快速幂我是直接抄的模板,刚开始时不理解,现在懂了,详情直接看代码

参考代码;
1 #include<iostream>
2 #include<cstdlib>
3 #include<cstdio>
4 #include<cstring>
5 #include<algorithm>
6 #include<cmath>
7 using namespace std;
8 struct prog {
9 int a[2][2] ;
10 void init(){
11 a[0][0]=a[1][0]=a[0][1]=1;
12 a[1][1]=0;
13 }
14 };
15
16 prog matrixmul ( prog a ,prog b )
17 {
18 int i , j , k ;
19 prog c ;
20 for ( i = 0 ; i < 2; i ++ )
21 {
22 for ( j = 0 ; j < 2 ; j ++ )
23 {
24 c.a[i][j]=0;
25