Number Sequence(sdut2044

Number Sequence

Time Limit: 1000MS    Memory limit: 65536K

题目描述

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).

输入

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.

输出

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

示例输入

1 1 3
1 2 10
0 0 0

示例输出

2
5

 

分析：

循环节，f(n-1)和f(n-2)各有7种情况，最多7*7=49种可能，。。。

 

#include<stdio.h>
int s[55]={0,1,1};
int main()
{
    int n,a,b,i;
    while(scanf("%d%d%d",&a,&b,&n),a!=0)
    {
        for(i=3;i<=51;i++)
        {
            s[i]=(a*s[i-1]+b*s[i-2])%7;
            if(s[i-1]==1&&s[i]==1)
            {
                break;
            }
        }
        printf("%d\n",s[n%(i-2)]);
    }
    return 0;
}