https://codeforces.com/problemset/status?
思路：
板子
#include<iostream>
#include<vector>
#include<queue>
#include<cstring>
#include<cmath>
#include<map>
#include<set>
#include<cstdio>
#include<algorithm>
#define debug(a) cout<<#a<<"="<<a<<endl;
using namespace std;
const int maxn=2e5+1000;
typedef long long LL;
inline LL read(){LL x=0,f=1;char ch=getchar(); while (!isdigit(ch)){if (ch=='-') f=-1;ch=getchar();}while (isdigit(ch)){x=x*10+ch-48;ch=getchar();}
return x*f;}
LL dp[20][4];
LL a[20];
LL dfs(LL pos,LL tot,bool limit){
if(!pos) return 1;
if(!limit&&dp[pos][tot]!=-1) return dp[pos][tot];
LL up=limit?a[pos]:9;
LL res=0;
for(int i=0;i<=up;i++){
if(tot==3&&i) continue;
if(i!=0) res+=dfs(pos-1,tot+1,limit&(i==up));
else if(i==0) res+=dfs(pos-1,tot,limit&(i==up));
}
if(!limit) dp[pos][tot]=res;
return res;
}
LL query(LL x){
LL cnt=0;
while(x>0){
a[++cnt]=x%10;
x/=10;
}
LL sum=dfs(cnt,0,1);
return sum;
}
int main(void){
LL t;cin>>t;
while(t--){
memset(dp,-1,sizeof(dp));
LL l,r;cin>>l>>r;
cout<<query(r)-query(l-1)<<"\n";
}
return 0;
}