Problem 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
https://blog.csdn.net/power721/article/details/5861487
#include<stdio.h>
int result[1000000];
int n;
int count = 0;
void search(int k,int sum) {
for (int i = 1; i < n; i *= 2) {
if (i >= result[k - 1]) { //保证比前一个数大
result[k] = i;
if (sum + i >= n) {
if (sum + i == n)
count++;
}
else
search(k + 1, sum + i);
}
}
}
int main() {
scanf("%d", &n);
search(1, 0);
printf("%d", count);
return 0;
}