数学问题通常暴力的话会超时,规律自己又找不到,这类问题实际不好搞....
#include<cstdio>
int main()
{
int n,a=1,ans=0;
int left,now,right;
scanf("%d",&n);
while(n/a!=0)
{
left=n/(a*10);
now=n/a%10;
right=n%a;
if(now==0) ans+=left*a;
else if(now==1) ans+=left*a+right+1;
else ans+=(left+1)*a;
a*=10;
}
printf("%d\n",ans);
return 0;
}