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
Source
USACO 2005 January Silver
个人理解：
只要找出规律即可。
代码：
#include<stdio.h>
int a[1000001];
int main()
{
a[1]=1;
a[2]=2;
int n,i=3;
while(i<1000001){
a[i++]=a[i-1];
a[i++]=(a[i-1]+a[i/2])00000000;
}
scanf("%d",&n);
printf("%d\n",a[n]);
return 0;
}
