玲珑杯 A 枚举 思维 数学

#include <bits/stdc++.h>
using namespace std;
int main()
{
int n;
cin>>n;
double  ans=-3;
double a;
double maxn=-2;
for(int i=2;i<=n-1;i++)
{
if(i%2==0)
{
a=2*sin(i/2.0)+sin(n-i);
}
else
{
maxn=max(maxn,cos((i-2)/2.0));
a=2*sin(i/2.0)*maxn+sin(n-i);
}
ans=max(ans,a);
}
printf("%.9f\n",ans );
}