c语言程序设计之累加求和

#include <stdio.h>
int main()
{
    double s=1,x,item,t=1,b=1;
    int n,i,flag = 1;
    scanf("%lf%d",&x,&n);
    for(i=2;i<=n;i++)
    {
        t*=x;
        b*=i-1;
        item = t/b;
        s += item * flag;
        flag *= -1;
    }
    printf("%lf",s);

    return 0;
}