本来想每次模7就够了,但这样忽略了数据量的庞大,规律如下:
因为模总是在0~6之间,所以f(i-1)与f(i-2)也是如此,每种有七种情况,所以公式就有7X7=49种情况,49为一循环
代码如下:
#include<stdio.h>
int f[100000005];
int main()
{
f[1]=1;
f[2]=1;
int i,p,q,n;
while(~scanf("%d%d%d",&p,&q,&n)&&(p||q||n))
{
for(i=3;i<=49;i++)
{
f[i]=(p*f[i-1]+q*f[i-2])%7;
}
printf("%d\n",f[n%49]);
}
}
题目如下:
Number Sequence
Time Limit: 2000/1000 MS (Java/Others) Memory Limit: 65536/32768 K (Java/Others)
Total Submission(s): 140179 Accepted Submission(s): 33985
Problem 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
Sample Output