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
1
2
3
0
Sample Output
1
7
20
一般这种让根据公式求出对应项的值得题都有规律 （有一个循环，此题的循环为4018（注意 这种有循环规律的是让你输出对应项对某个数取余后的题））可以先打表写出有限个数的结果，再观察规律，或者直接写代码判断是否进入了循环。
import java.math.BigDecimal; import java.util.Scanner; public class Main { static int[] f = new int[10000]; public static void main(String[] args) { f[1]=1; f[2]=7; for(int i=3;i<=4018;i++){ f[i] = (f[i-2]-((i-1)*(i-1)*(i-1))+(i*i*i))%2009; //System.out.println(i+" "+f[i]); } Scanner sc = new Scanner(System.in); while(sc.hasNext()){ int n = sc.nextInt(); if(n==0) return ; // for(int i=3;i<100000;i+=2){ // if(f[i]==1&&f[i+1]==7){ // System.out.println(i-1); // break; // } // } //判断多久开始循环 System.out.println(f[n%4018]); } } }
