Question

c语言编写函数求表达式的和（n的值由主函数输入）。1-1/2+1/3-1/4+......+1/m

#include <stdio.h>
void wwjt();

double sum(int n)
{
/**********Program**********/

/********** End **********/
}

main()
{
int n;
scanf("%d",&n);
printf("sum=%f\n",sum(n));
wwjt();
}

void wwjt()
{
FILE *IN,*OUT;
int n;
int i[10];
double o;
IN=fopen("in.dat","r");
if(IN==NULL)
{
printf("Read FILE Error");
}
OUT=fopen("out.dat","w");
if(OUT==NULL)
{
printf("Write FILE Error");
}
for(n=0;n<5;n++)
fscanf(IN,"%d",&i[n]);
for(n=0;n<5;n++)
{
o = sum(i[n]);
fprintf(OUT,"%f\n",o);
}
fclose(IN);
fclose(OUT);
}

Answer 1

double sum(int n)
{
double s=0,sign=1;
int i;
for(i=1;i<=n;i++)
{
s+=sign/i;
sign=-sign;
}
return s;
}

Answer 2

double s=0;
int i,k=1;
for(i=1;i<=n;i++)
{
s=s+k*1.0/i;
k=-k;
}
return(s);