Number Sequence【规律】

Number Sequence

Time Limit:1000MS     Memory Limit:32768KB     64bit IO Format:%I64d & %I64u

Description
A number sequence is defined as follows: 

f(1) = 1, f(2) = 1, f(n) = (A * f(n - 1) + B * f(n - 2)) mod 7. 

Given A, B, and n, you are to calculate the value of f(n).

 

Input

The input consists of multiple test cases. Each test case contains 3 integers A, B and n on a single line (1 <= A, B <= 1000, 1 <= n <= 100,000,000). Three zeros signal the end of input and this test case is not to be processed. 

Output

For each test case, print the value of f(n) on a single line. 

Sample Input
1 1 3
1 2 10

0 0 0

Sample Output
2

5

【思路】多找些数据观察规律(每48组数据一个循环)

AC代码：

#include
int main()
{
	int a, b, n, f[50]={0, 1, 1};
	while(scanf("%d %d %d", &a, &b, &n))
	{
		if( !(a+b+n) ) break;
		n %= 48;
		for(int i = 3; i <= 50; i++)
			f[i] = (f[i-1]*a + f[i-2]*b) % 7;
		printf("%d\n", f[n]);
	}
	return 0;
}