zoj 3405 Counting Factor Trees

zoj 3405 Counting Factor Trees

#include <iostream>#include <cstdio>#include <vector>#include <algorithm>#include <queue>#include <cmath>#include <string>#include <string.h>#include <cstdlib>#define MAXN 100000#define bignum unsigned long longusing namespace std;bignum c[64][64];bool f[100005];int a[100005],an=0;int ans[50],ansn;void init(){ int i,j; for(i=0;i<64;i++){ for(j=0;j<=i;j++){  c[i][j]=(j==0)?1:c[i-1][j-1]+c[i-1][j]; } } f[1]=true; for( i=2;i<=MAXN;i++) if(!f[i]){ a[an++]=i; for(j=2*i;j<=MAXN;j+=i){ f[j]=true; } }}int main(){ int n;init();while(scanf("%d",&n)!=EOF){ansn=0; for(int i=0;i<an;i++){ while(n%a[i]==0){ ans[ansn++]=i; n/=a[i]; } } if(n!=1){ ans[ansn++]=n; } bignum ss=1; int i,j=1,sum=ansn; for (i=1;i<ansn;i++) { if(ans[i]==ans[i-1]) j++; else  { ss*=(bignum)c[sum][j]; sum-=j; j=1; } } ss*=(bignum)c[sum][j]; sum=ansn-1; printf("%llun",c[2*sum][sum]/(sum+1)*ss);} return 0;}