hdu 3709 Balanced Number 数位DP

#include<cstdio>
#include<cstring>
#include<algorithm>
#define ll __int64
using namespace std;
int bit[20];
ll dp[20][20][2000];
ll dfs(int pos,int pre,int o,bool f)
{
if(pos==-1) return pre==0;
if(!f&&dp[pos][o][pre]!=-1) return dp[pos][o][pre];
ll ans=0;
int e=f?bit[pos]:9;
for(int i=0;i<=e;i++)
ans+=dfs(pos-1,pre+i*(pos-o),o,f&&(i==bit[pos]));
if(!f) dp[pos][o][pre]=ans;
return ans;
}
ll cal(ll n)
{
int m=0;
while(n){
bit[m++]=n%10;
n/=10;
}
ll ans=0;
for(int o=0;o<m;o++)
ans+=dfs(m-1,0,o,1);
return ans-(m-1);
}
int main()
{
ll n,m;
int t;
memset(dp,-1,sizeof(dp));
scanf("%d",&t);
while(t--){
scanf("%I64d%I64d",&n,&m);
printf("%I64d\n",cal(m)-cal(n-1));
}
}