C語言練習-迭代

float added(int n)
{
    float i,res;
    int flag=1;
    for(i=1;i<n;i=i+2)
    {
        res += flag*i/(i+2);
        flag = (-1)*flag;
    }
    return res;
}

float added_2(int n)      // res always = 1   >>flag should be float, otherwise the div result always is 0
{
    int i,m=1;
    float sum=0,flag=1;
    for(i=0;i<=n;i++)
    {
        sum = sum + flag/m;
        m *= 2;
        flag= -flag;
    }

    return sum;
}

float added_3(int n)
{
    int i,m=1;
    float sum=0,flag=1;
    for(i=1;i<=n;i++)
    {
        m *= i;
        sum = sum + flag/m;

        flag= -flag;
    }

    return sum;
}

/* 2 + 22 + 222 + 2222 + ....*/
void Iteration()
{

    int a,n,count=1,Sn=0,Tn=0;
    printf("Enter a and n:\n");
    scanf("%d %d",&a,&n);
    while (count<=n )
    {
        Tn=Tn*10+a;
        Sn=Sn+Tn;
        count++;
    }
    printf("a+aa+aaa+...=%d\n",Sn);

}