没错，又是我，国庆别放松哦

供参考：

 #include<stdio.h>
 int main()
 {
     int n,i=1;
     double s=0,fu=1,t;
     printf("请输入一个正整数n:");
     scanf("%d",&n);
     while(i <= 2*n)
     {
         t = 1.0*fu/i;
         s += t;
         fu = -fu;
         i++;
     }
     printf("s=%f",s);
     
     return 0;
 }

#include<stdio.h>
int main()
{
    float s = 0;
    int n;
    printf("请输入一个正整数：");
    scanf("%d",&n);
    int i = 1;
    while(i<=8)
    {
        s += 1.0/(2*i-1) - 1.0/(2*i);
        i++;
    }
    printf("\ns = %f",s);
     return 0;
}