C语言解答

int main(int argc, char* argv[])
{
	int sum,i,a,n;
	while(~scanf("%d",&n))
	{
		sum=0;a=0;
	  for(i=1;i<=n;i++)
	  { 
		  sum+=a*10+2;
		  a=a*10+2;
	  }
	  printf("%d\n",sum);
	}
	return 0;
}

C++解答

#include<iostream>
#include<iomanip>
#include<fstream>
#include<string> 
#include<climits>
#include<cctype>
#include<cmath>
#include<cstring>
using namespace std;

int main()
{
 //ifstream cin("aaa.txt");
  int i,j,n,m,k,sum,p,len,a[1000],l,count;
  
  int x,y;
  string s,b[1000];
  cin>>n;
  memset(a,0,sizeof(a));
 
  for(i=1;i<=n;i++)
  {
	  a[i]=2*(n+1-i);
  }
   for(i=1;i<=n;i++)
   {
	   a[i+1]+=a[i]/10;
	   a[i]=a[i]%10;
   }
   while(a[n]>=10)
   {
     a[n+1]=a[n]/10;
	   a[n]=a[n]%10;
	   n++;
   }
   for(i=n;i>=1;i--)
	   cout<<a[i];
   cout<<endl;
  

  	return 0;

}