题解:
#include<stdio.h>
#include<algorithm>
using namespace std;
typedef long long ll;
#define maxn 1000005
ll a[maxn];
ll bit(ll x)
{
if(x==0)
return 1;
ll cnt=0;
while(x)
cnt++,x/=10;
return cnt;
}
bool comp(ll a,ll b)
{
return a>b;
}
int main(void)
{
int n;
ll ans=0;
scanf("%d",&n);
for(int i=1;i<=n;i++)
{
scanf("%lld",&a[i]);
ans-=(n-i)*bit(a[i]);
}
sort(a+1,a+n+1,comp);
for(int i=1;i<=n-1;i++)
{
int l=i+1,r=n;
ll now=bit(a[i]);
while(l<=r)
{
int mid=(l+r)/2;
if(bit(a[i]+a[mid])>now)
l=mid+1;
else
r=mid-1;
}
ans+=(r-i)*(now+1)+(n-r)*now;
}
printf("%lld\n",ans);
return 0;
}