POJ 2992 因子个数

Divisors

Time Limit: 1000MS		Memory Limit: 65536K

Description

Your task in this problem is to determine the number of divisors of  C_n^k. Just for fun -- or do you need any special reason for such a useful computation?

Input

The input consists of several instances. Each instance consists of a single line containing two integers n and k (0 ≤ k ≤ n ≤ 431), separated by a single space.

Output

For each instance, output a line containing exactly one integer -- the number of distinct divisors of  C_n^k. For the input instances, this number does not exceed 2 ⁶³ - 1.

Sample Input

5 1
6 3
10 4

Sample Output

2
6
16

题意：给你n和k，求C(K,N)(K<=N)的约数有多少个。

题解：先筛选出431之内的素数，然后对每个阶乘进行素因子分解，求组合数的素因子分解即可。

#include
#include
#include
#include
using namespace std;
int main(){
	bool boo[440];
	int p[85],k=0;
	memset(boo,0,sizeof(boo));
	boo[0]=boo[1]=0;
	for(i=2;i<440;i++){//素数
		if(!boo[i])p[k++]=i;
		for(j=0;j