HDU 2011 多项式求和

#include<stdio.h>
int main()
{
int s,n,i;
double sum,t;
scanf("%d",&s);
while(s--)
{
sum=0;
scanf("%d",&n);
for(i=1;i<=n;i++)
{
if(i%2==1)
{
sum=sum+(double)(1.0/i);
}
if(i%2==0)
{
sum=sum-(double)(1.0/i);
}
}
printf("%.2lf\n",sum);
}
return 0;
}