没错，又是我，国庆别放松哦

Question

Answer 1

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;
 }