OJ-Problems-Source/HDOJ/4066_autoAC.cpp

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#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<algorithm>
using namespace std;
const int maxn=1510;
double a[maxn], d[maxn];
void getd()
{
d[1]=0.5;
for(int i=2; i<maxn; i++)
d[i]=d[i-1]*(2*i-1)/(2*i);
}
void geta()
{
a[0]=1.0;
for(int i=1; i<maxn; i++)
a[i]=a[i-1]+2*d[i];
}
int main()
{
getd();
geta();
int t, ca=1, n;
scanf("%d", &t);
while(t-->0)
{
scanf("%d", &n);
printf("Case %d: ", ca++);
if(n&1)
printf("%.6lf\n", a[n/2]);
else
printf("%.6lf\n", (a[(n-1)/2]+a[(n+1)/2])*0.5);
}
return 0;
}