第二章例2-8

/* 计算1-1/3+1/5-1/7+… 共n项之和 */

#include<stdio.h>

int main(void)

{

    int denominator,flag,i,n;

    double item,sum;

    printf("Enter n:");

    scanf_s("%d",&n);

    flag=1;

    denominator=1;

    sum=0;

    for(i=1;i<=n;i++){

        item=flag*1.0/denominator;

        sum=sum+item;

        flag=-flag;

        denominator=denominator+2;
    }
    printf("sum=%f\n",sum);

    return 0;

}