杭电acm 2802F(N)（循环节）

F(N)

ime Limit: 2000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 5055    Accepted Submission(s): 1801

Problem Description

Giving the N, can you tell me the answer of F(N)?

 

Input

Each test case contains a single integer N(1<=N<=10^9). The input is terminated by a set starting with N = 0. This set should not be processed.

 

Output

For each test case, output on a line the value of the F(N)%2009.

 

Sample Input

1230

 

Sample Output

1720

 

Source

HDU 2009-4 Programming Contest

想法：打表+数学思维（循环节）

代码：

#include<stdio.h>
#include<string.h>
#define maxn 2009
int a[100010];
void init()
{
    int i;
    a[1]=1;a[2]=7;
    for(i=3;i<=5000;i++)
    {
      a[i]=(a[i-2]+i*i*i-(i-1)*(i-1)*(i-1))%maxn;
    }


}
int main()
{
   int n;
   init();
   while(scanf("%d",&n)&&n!=0)
   {
        n=n%4018;
       printf("%d\n",a[n]);
   }
   return 0;
}