HDU 3709 Balanced Number

#include<bits/stdc++.h>
using namespace std;
#define MS1(a) memset(a,-1,sizeof(a))
#define MS0(a) memset(a,0,sizeof(a))
typedef long long ll;
int bit[23];
ll dp[20][1800][20];
ll dfs(int pos,int val,int pivot,bool edge)
{
    if(val < 0) return 0;
    if(pos == -1) return val == 0;
    if(!edge && dp[pos][val][pivot] >= 0) return dp[pos][val][pivot];
    int end = edge ? bit[pos] : 9;
    ll ans = 0;
    for(int i = 0;i <= end;i++){
        ans += dfs(pos - 1,val+i*(pos - pivot),pivot,edge&&(i==end));
    }
    if(!edge) dp[pos][val][pivot] = ans;
    return ans;
}
ll calc(ll n)
{
    if(n == -1) return 0;
    int tot = 0;
    while(n){
        bit[tot++] = n%10;
        n /= 10;
    }
    ll ans = 0;
    for(int i = tot - 1;i >= 0;i--)
        ans += dfs(tot - 1,0,i,true);
    return ans - tot + 1;
}
int main()
{
    MS1(dp);
    int T;
    scanf("%d",&T);
    while(T--){
        ll L,R;
        scanf("%I64d%I64d",&L,&R);
        printf("%I64d\n",calc(R) - calc(L-1));
    }
}