计算s=3+33+333+···n个33···3,n由主函数输出，int f(int n) 用累加的方式求和

#include
int f(int n)
{
int i,sum = 0;
int temp = 3;
for(i=1;i<=n;i++)
{
sum += temp;
temp *= 10;
temp += 3;
}
return sum;
}

int main()
{
int i;
while(scanf("%d",&i)==1)
{
printf("%d\n",f(i));
}
}

#include

int f(int n)
{
if (1 == n) return 3;
return f(n - 1) * 10 + 3;
}

int main(void)
{
int n, i;
long sum = 0;

scanf("%d", &n);
for (i = 1; i <=n; i++)
sum += f(i);

printf("%d\n", sum);
return 0;
}

#include
int f(int n)
{int t=0,s=0;
for(int i=1;i<=n;i++)
{ t=10*t+3;
s=s+t;
}
return s;
}
int main()
{
int i;
while(scanf("%d",&i)==1)
{
printf("%d\n",f(i));
}
}