#include <stdio.h>
int main(void)
{
int flag, i, n, t;
int repeat, ri;
double item, sum;
scanf("%d", &repeat);
for(ri = 1; ri <= repeat; ri++){
scanf("%d", &n);
sum=0.0;
for(t=0;t<=n;t++){
if (t%2==1)
i=-1;
else i=1;
sum=sum+(double)i/(1+3*t);
}
printf("sum = %.3f\n", sum);
}
}
这样编错在何处?为什么t++与++t的结果没有区别?求高手解答。。