poj 3595 Full Steiner Topologies

poj 3595 Full Steiner Topologies

#include <iostream>#include <cmath>using namespace std;const double PI=acos(-1.0);const double e=exp(1.0);int n;int main(){while(scanf("%d",&n)!=-1){int tn,num,i;double sum,n1,n2,n3;if(n<=10){tn=n;sum=1;while(2*tn-5>0){sum=sum*(2*tn-5);tn--;}for(i=0;sum>10;i++){sum=sum/10;}printf("%.3lfE%dn",sum,i);continue;}tn=2*n-5;n1=0.5*log(2*PI*tn)+tn*(log(tn*1.0)-1)+(1.0/(12.0*tn));tn=n-3;n2=0.5*log(2*PI*tn)+tn*(log(tn*1.0)-1)+(1.0/(12.0*tn));n3=(n-3)*log(2.0);n1=n1-n2-n3;n1=n1*log10(e);num=n1;n1=modf(n1,&n2);n1=pow(10,n1) ;printf("%.3lfE%dn",n1,num);}return 0;}