Question

求C语言大神帮忙

求C语言大神帮忙求交错序列前n项和：输入一个整数n,计算交错数列1－2／3＋3／5－4／7+……

Answer 1

#include<stdio.h>
main()
{
    int a=1,b=1;
    double m,s=0;
    int i=1,n;
    scanf("%d",&n);
    while(i<=n)
    {
        m=(double)a/b;
        if(a%2)
             s+=m;
        else s+=-m;
        a+=1;
        b=2*a-1;
        i++;
    }
    printf("%lf",s);
}

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Answer 2

#include<stdio.h>

int main()
{
int n,i;
scanf("%d",&n);
double sum = 0,ok = 1.0;
for(i = 1;i<=n;i++) {
sum += ok * i/(2*i-1);
ok *= -1;
}
printf("%lf\n",sum);
return 0;

}