SCU 2009（数位dp）

#include <iostream>
#include <cstdio>
#include <cmath>
#include <cstdlib>
#include <algorithm>
#include <cstring>
#include <queue>
#include <vector>
#define LL long long
#define N 3000010
using namespace std;
int n,k;
LL dp[70][70][105];
LL dfs(int pos,int num,int md,int fzore)
{
    if(!pos)
    {
        return num==n/2&&!md;
    }
    if(~dp[pos][num][md])return dp[pos][num][md];
    LL ans=0;
    for(int i=0;i<=1;i++)
    {
        if(fzore)
        {
            if(i==1)ans+=dfs(pos-1,num+1,(md*2+i)%k,0);
        }
        else
        {
            if(i==1)ans+=dfs(pos-1,num+1,(md*2+i)%k,0);
            else ans+=dfs(pos-1,num,(md*2+i)%k,0);
        }
    }
    dp[pos][num][md]=ans;
    return ans;
}
int main()
{
    int T,cas=1;

    scanf("%d",&T);
    while(T--)
    {
        scanf("%d%d",&n,&k);
        printf("Case %d: ",cas++);
        memset(dp,-1,sizeof(dp));
        if(k==0||n%2==1)
        {
            puts("0");continue;
        }
        printf("%lld\n",dfs(n,0,0,1));
    }
}