題意：在n到m區間內，有多少個數滿足每位數字非零的不超過3個（前導零無關）。

#include<iostream>
#include<cstdio>
#include<cstring>
#include<cstdlib>
#include<algorithm>
#include<queue>
#include<vector>
#include<stack>
#include<map>
#include<set>
#include<cmath>
#include<cctype>
#include<ctime>
#define INF 0x3f3f3f3f
#define PI acos(-1.0)
typedef long long ll;
typedef unsigned long long ull;

using namespace std;

int a[25];
ll dp[25][25];

ll dfs(int len,int sum,bool limit)
{
	if(len==-1) return sum<4;
	if(!limit&&dp[len][sum]!=-1) return dp[len][sum];
	ll ans=0;
	int up=limit?a[len]:9;
	for(int i=0;i<=up;i++)
	{
		ans+=dfs(len-1,sum+(i!=0),i==a[len]&&limit);
	}
	if(!limit) dp[len][sum]=ans;
	return ans;
}

ll fun(ll x)
{
	int len=0;
	while(x)
	{
		a[len++]=x%10;
		x/=10;
	}
	return dfs(len-1,0,1);
}

int main()
{
    ll n,m,t;
    cin>>t;
    while(t--)
    {
    	cin>>n>>m;
    	memset(dp,-1,sizeof(dp));
    	cout<<fun(m)-fun(n-1)<<endl;
	}
    return 0;
}