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
譯:
問題描述
農夫約翰命令他的牛尋找不同的數字集合,這些數字和一個給定的數字。奶牛隻使用整數冪爲2的數字。下面是可能的數字集合,它們的和是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
幫助FJ計算一個給定整數N的所有可能表示形式(1 <= N <= 1,000,000)。
輸入
一行只有一個整數N。
輸出
表示N的方法的個數作爲表示的和。由於這個數字可能很大,所以只打印最後9位數字(以10爲基數表示)。
樣例輸入
7
樣例輸出
6
#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]) { //保證比前一個數大
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;
}