#include <stdio.h>
int main(void)
{
    double sums_1,sums_2;
    int sign,times,n;
    n=1;
    printf("Please input the number of times you want\n");
    scanf("%d",&times);
    for(sums_1=0.0,sums_2=0.0;n<=times;n++)
    {
        sums_1+=1.0/(double)n;
        for(sign=1;sign<=n;sign++)
            sign*=-1;
        sums_2+=sign*1.0/(double)n;
    }
        printf("The result of %d times is %lf and %lf\n",times,sums_1,sums_2);
        return 0;
}


编译环境VC++6.0

输入后无结果显示，编译没有报错

已经改正

#include <stdio.h>
int main(void)
{
    double sums_1,sums_2;
    int sign,times,n;
    sign=1;
    sums_1=0.0,sums_2=0.0;
    printf("Please input the number of times you want\n");
    scanf("%d",&times);
    for(n=1;n<=times;n++)
    {
        sums_1+=1.0/n;
        sums_2+=sign*1.0/n;
        sign*=-1;
    }
        printf("The result of %d times is %lf and %lf\n",times,sums_1,sums_2);
        return 0;
}
原因符号没有控制好，思路不够清晰

[ 本帖最后由 小小熊宝宝 于 2010-9-10 13:02 编辑 ]

for(sign=1;sign<=n;sign++)
            sign*=-1;
sign的值只有0和1

for(sign=1;sign<=n;sign++)
        { sign*=-1;
        }
        sums_2+=sign*1.0/(double)n;
这里你不应该这么弄printf("The result of %d times is %lf and %lf\n",times,sums_1,sums_2);
这里的sum_2会是0 因为‘1f‘ .
至于你说的为什么没有输出 我调试了下也不知道为什么 ，