F(N)
Time Limit: 2000/1000 MS (Java/Others) Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 4078 Accepted Submission(s):
1432
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
#include<stdio.h>
#include<string.h>
#include<algorithm>
#include<math.h>
#define LL long long
#define MAX 10010
using namespace std;
LL s[MAX];
LL p[MAX];
void biao()
{
int i,j;
s[1]=p[1]=1;
s[2]=p[2]=7;
for(i=3;i<=4020;i++)
{
s[i]=s[i-2]+pow(i,3)-pow((i-1),3);
p[i]=s[i]%2009;
}
}
int main()
{
int n,m,i,j;
biao();
while(scanf("%d",&n),n)
{
printf("%lld
",p[n%4018]);
}
return 0;
}