BZOJ1087【状压DP】

又一发【科学】的代码风格.

/* I will wait for you */

#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <ctime>
#include <algorithm>
#include <iostream>
#include <fstream>
#include <vector>
#include <queue>
#include <deque>
#include <set>
#include <map>
#include <string>
#define make make_pair
#define fi first
#define se second

using namespace std;

typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> pii;

const int maxn = 520;
const int maxm = 1010;
const int maxs = 26;
const int inf = 0x3f3f3f3f;
const int P = 1000000007;
const double error = 1e-9;

inline int read()
{
	int x = 0, f = 1; char ch = getchar();
	while (ch < '0' || ch > '9') f = (ch == '-' ? -1 : 1), ch = getchar();
	while (ch >= '0' && ch <= '9') x = x * 10 + ch - '0', ch = getchar();
	return x * f;
}

int n, k, allow[maxn], sum[maxn], h[maxn][maxn];
ll ans, f[10][100][maxn];

void init() 
{
	for (int i = 0; i < (1 << n); i++) {
		if (! (i & (i << 1))) {
			 for (int j = i; j; j >>= 1) sum[i] += (j & 1);
			 allow[i] = 1;
		}
	}
	
	for (int i = 0; i < (1 << n); i++) if (allow[i])
		for (int j = 0; j < (1 << n); j++) if (allow[j])
			if (! (i & j) && ! ((i >> 1) & j) && ! (i & (j >> 1)))
				h[i][j] = 1;
}

int main()
{
	n = read(), k = read(), init();
	
	for (int i = 0; i < (1 << n); i++) 
		if (allow[i]) f[0][sum[i]][i] = 1;
	
	for (int i = 0; i < n - 1; i++) 
		for (int x = 0; x < (1 << n); x++) if (allow[x])
			for (int y = 0; y < (1 << n); y++) if (allow[y])
				if (h[x][y])
					for (int s = sum[x]; s + sum[y] <= k; s++)
						f[i + 1][s + sum[y]][y] += f[i][s][x];
		
	for (int i = 0; i < (1 << n); i++)
		ans += f[n - 1][k][i];
		
	printf("%lld\n", ans);

	return 0;
}