位数差（二分）
AC_Code
1 #include <bits/stdc++.h> 2 using namespace std; 3 typedef long long ll; 4 const int maxn = 1e5+5; 5 const int inf=0x3f3f3f3f; 6 #define rep(i,first,last) for(int i=first;i<=last;i++) 7 #define dep(i,first,last) for(int i=first;i>=last;i--) 8 9 int a[maxn]; 10 int bit(int x){ 11 int ans=0; 12 if( x==0 ) return 1; 13 while(x){ 14 ans++; 15 x/=10; 16 } 17 return ans; 18 } 19 bool cmp(int x, int y){ return x>y; } 20 21 int main() 22 { 23 int n; 24 scanf("%d",&n); 25 ll ans=0; 26 rep(i,1,n){ 27 scanf("%d",&a[i]); 28 ans-=(n-i)*bit(a[i]); 29 } 30 sort(a+1,a+1+n,cmp); 31 rep(i,1,n-1){ 32 int l=i+1,r=n; 33 ll now=bit(a[i]); 34 while( l<=r ){ 35 int mid=(l+r)>>1; 36 if( bit(a[i]+a[mid])>now ) l=mid+1; 37 else r=mid-1; 38 } 39 ans += (r-i)*(now+1)+(n-r)*now; 40 } 41 printf("%lld\n",ans); 42 return 0; 43 }
