紫书 习题 10-15 UVa 12063（数位dp）

大佬真的强！！https://blog.csdn.net/u014800748/article/details/45225881

#include<cstdio>
#include<cstring>
#define REP(i, a, b) for(int i = (a); i < (b); i++)
using namespace std;

typedef long long ll;
const int MAXN = 70;
int mod[MAXN], n, k;
ll d[MAXN][MAXN][MAXN*2];

ll dfs(int cur, int num, int MOD)
{
	if(cur == 0)
	{
		if(num > 0) return 0;
		return d[cur][num][MOD] = (MOD % k == 0);
	}
	if(d[cur][num][MOD] != -1) return d[cur][num][MOD];

	ll& ans = d[cur][num][MOD];
	ans = dfs(cur - 1, num, MOD);
	if(num > 0) ans += dfs(cur - 1, num - 1, (MOD - mod[cur] + k) % k);
	return ans;
}

void init()
{
	mod[1] = 1;
	REP(i, 2, MAXN)
		mod[i] = (mod[i-1] << 1) % k;
}

int main()
{
	int T, kase = 0;
	scanf("%d", &T);

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

	return 0;
}