POJ 2229 Sumsets

http://poj.org/problem?id=2229

Sumsets

Time Limit: 2000MS		Memory Limit: 200000K
Total Submissions: 15492		Accepted: 6165

Description

Farmer John commanded his cows to search for different sets of numbers that sum to a given number. The cows use only numbers that are an integer power of 2. Here are the possible sets of numbers that sum to 7: 

1) 1+1+1+1+1+1+1 
2) 1+1+1+1+1+2 
3) 1+1+1+2+2 
4) 1+1+1+4 
5) 1+2+2+2 
6) 1+2+4 

Help FJ count all possible representations for a given integer N (1 <= N <= 1,000,000). 

Input

A single line with a single integer, N.

Output

The number of ways to represent N as the indicated sum. Due to the potential huge size of this number, print only last 9 digits (in base 10 representation).

Sample Input

7

Sample Output

6

#include <stdio.h>
#include <string.h>
int a[1000000+10];
void fun(int N)
{
	a[1]=1;a[2]=2;
	for(int i=3;i<=N;++i)
	{
		if(i&1) a[i]=a[i-1];
		else a[i]=a[i-1]+a[i/2];
		a[i]%=1000000000;
	}
}
int main()
{
	int N;
	while(~scanf("%d",&N))
	{
		fun(N);
		printf("%d\n",a[N]);//
	}
}