动态规划_Sumsets_POJ-2229

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<iostream>
using namespace std;
int d[1000005];
int main()
{
    int i,n;
    d[1]=1;
    d[2]=2;
    for(i=3;i<=1000000;i++) {
        if(i&1)
            d[i]=d[i-1];
        else
            d[i]=(d[i-2]+d[i/2])%1000000000;
    }
    cin>>n;
    cout<<d[n]<<endl;
    
    return 0;
}