2019年华南理工大学程序设计竞赛（春季赛）A NB群友

#include<bits/stdc++.h>

using namespace std;
#define ll long long
map<ll , ll >dp;
const int mod = 1e9 + 7;
ll dfs(ll x)
{
    if(x<1) return 0;
    if(dp[x]) return dp[x];
    ll ans=0;
    for(int i=2 ; i<=9 ; i++)
    {
        ll now=x/i;
        if(now>=1) ans++;
        ans+=dfs(now);///累记记忆化搜索的值
        ans%=mod;
    }
   return dp[x]=ans;
}

int main() {
   int t; scanf("%d",&t);

   while(t--)
   {
       ll l ,r;scanf("%lld%lld",&l,&r);
       dp.clear();
       ll sum1 = dfs(r);
       dp.clear();
       ll sum2 =dfs(l-1);
       printf("%lld\n",(sum1-sum2+mod)%mod);
   }
    return 0;
}