Balanced Number HDU - 3709

http://acm.hdu.edu.cn/showproblem.php?pid=3709

dp[i][j]代表[i+1,pos-1]的权值和为j时 [0,i]能提供多少解

#include <cstdio>
#include <cstring>
#include <algorithm>
using namespace std;
typedef long long ll;
const int maxn=20;
const int maxm=2000;

ll dp[maxn][maxm];
int bit[maxn];

ll dfs(int pos,int mid,int sta,int limit)
{
    ll res;
    int up,i;
    if(pos==-1) return sta==0;
    if(sta<0) return 0;
    if(!limit&&dp[pos][sta]!=-1) return dp[pos][sta];
    if(limit) up=bit[pos];
    else up=9;
    res=0;
    for(i=0;i<=up;i++){
        res+=dfs(pos-1,mid,sta+i*(pos-mid),limit&&i==bit[pos]);
    }
    if(!limit) dp[pos][sta]=res;
    return res;
}

ll solve(ll val)
{
    ll res;
    int n,i;
    if(val==-1) return 0;
    n=0;
    while(val>0){
        bit[n++]=val%10;
        val/=10;
    }
    res=0;
    for(i=0;i<=n-1;i++){
        memset(dp,-1,sizeof(dp));
        res+=dfs(n-1,i,0,1);
    }
    return res-(n-1);
}

int main()
{
    ll l,r;
    int t;
    scanf("%d",&t);
    while(t--){
        scanf("%lld%lld",&l,&r);
        printf("%lld\n",solve(r)-solve(l-1));
    }
    return 0;
}